Update the integrated shell to deal with a null line which can be
triggered with CTRL-D.

Fixes gh-229

Fixes gh-230

Numerous updates to the Spring CLI, primarily for better embedded REPL
shell support:

* Refactor the CLI application to help separate concerts between the
  main CLI and the embedded shell. Both the CLI and embedded shell now
  delegate to a new `CommandRunner` to handle running commands. The
  runner can be configured differently depending depending on need.
  For example, the embedded shell adds the 'prompt' and 'clear'
  commands.

* Most `Command` implementations have been moved to sub-packages so that
  they can be co-located with the classes that they use.

* Option commands are now only used in the CLI, the embedded shell
  does not user them and details have been removed from the Command
  interface.

* The REPL shell has been significantly refactored to:
    - Support CTRL-C to cancel the running process. This is supported
      when running external commands and most internal commands.
    - Fork a new JVM when running commands (primarily for CTRL-C support
      but also for potential memory and classpath issues)
    - Change the "continue" trigger from `<<` to `\`
    - Support command completion of files
    - Add ANSI color output
    - Provide 'help' support for internal commands (such as 'clear')
    - Remove the now redundant `stop` command

Fixes gh-227

Ensure that '--cp' is replaced with a same length string to prevent
odd help text formatting.

This reverts commit e1605b46.

Usage:

$ gradle bootRun
...

Edit files in src/main/resources and see the changes live in a web app
(e.g. static resources in /static).

The old functionality of bootRun has been replaced (since it didn't add
a lot of value and also didn't expose any JMV argument setters of anything).
This new feature set is backed by any existing "run" task configuration.

In addition autodetects a main class if there is one in the project
sources, so no need for mainClassName = '...' in build.gradle.

Applies the 'application' plugin (so no need to declare that either).

Fixes gh-225

The AST transformation that processes @Grab annotations is driven once
per source file. Previously, this meant that if an app consisted of
multiple source files then multiple, discrete dependency resolutions
would be performed.

This commit updates AetherGrapeEngine to cache a previous resolution's
outcome and use its dependency to influence the outcome of subsequent
resolutions. For example if a one resolution results in spring-core
4.0.0.RELEASE being added to the classpath, subsequent resolutions
that depend upon spring-core will always get the 4.0.0.RELEASE
version. This is achieved by using the dependencies found by earlier
resolutions as dependency management configuration of the current
resolution. This removes the possibility of multiple versions of the
same dependency ending up on the classpath.

In addition to using the results of earlier resolutions to provide
dependency management configuration, default dependency management
configuration is also provided. This configuration is specified by
the springcli.properties file and ensures that, where Boot prescribes
certain versions of a dependency, that is the version that will be
resolved. For example, this ensures that spring-data-redis, which
depends upon Spring 3.1.4, pulls in the version of Spring that Boot
requires instead.

Fixes #224

Fixes #226

Actually System.in works fine, it's the output streams that get buffered.
We can fix it by diverting them for the duration of the command.

Fixes gh-217

Improves gh-218

Fixes gh-219

We might also want to rethink "!" as a shell exec command (since it means
something in a real shell and in JLine). E.g. use "exec" or something.

Partial fix for gh-220 (ideally we'd process the events and catch
and handle exceptions).

Related to gh-212

InitCommand remains for now, so that you can @Grab a jar with
custom commands if you so choose.

Contributes to gh-212

A typical cause of startup failure is an incorrectly configured
classpath. Previously the classpath used to launch the application
wasn't easy for a user to discover. This made problem diagnosis
difficult. This commit adds an application listener that, in the event
of a start error, logs the thread context class loader's classpath at
INFO level. The classpath is also logged at DEBUG level when an
application starts successfully.

In this commit we retain "init" as a command inside the ShellCommand
but not on the bash command line.

Seems to have an impact on performance so relevant to gh-212.

Update SpringApplication to run by default in 'headless' mode. This
prevents the AWT system from creating a Java icon (for example in the
OSX dock).

Also update builds to run tests in 'headless' mode.

Fixed gh-212 again

Fixes gh-214

...even if the CommandLineRunners fail and we drop to the error
handling path.

Fixes gh-211

This appears to be a significant improvement in performance
(checking for the existence of init.grooy is cheap, but compiling
it is expensive).

I'm going to say this fixes gh-212.

Affects gh-212

Fix JarEntryData to re-read the local header, rather than relying on
the central directory record.

This protects against the situation where a JAR file is written with an
'Extra Field Length' that is different in the local header to the
central directory header.

This appears to be the case with aspectj 1.7.4 which contains the
following central directory file header for ProceedingJoinPoint:

	50 4B 01 02     signature
	14 03           version made by
	0A 00           version required
	00 00           general
	08 00           compress methods
	0E 40 59 43     last modified
	2D 59 20 70     crc
	EC 00 00 00     csize
	8D 01 00 00     size
	2A 00           fname len
	00 00           ext field len
	00 00           file comment len
	00 00           disk num
	00 00           int file att
	00 00 A4 81     ext file att
	97 F3 00 00     relative offset of the local file header
	...             file name

and the following local header:

	50 4B 03 04     signature
	0A 00           version required
	00 00           general
	08 00           compress method
	0E 40 59 43     last modified
	2D 59 20 70     crc
	EC 00 00 00     csize
	8D 01 00 00     size
	2A 00           fname len
	14 00           ext field len
	...             file name
	...             extra field

Note that the 'ext field len' is 0x00 in the central record but 0x14 in
the local record.

Fixes gh-203

Revert commit fd15b62a to
ensure that we don't accidentally use Java 8 features.

Replace references to 'files' throughout the code-base with 'sources'
following the rename of `FileOptions` to `SourceOptions`.

Also cleanup ResourceUtils a little