GroovyWebConfiguration creates a GroovyTemplateViewResolver which is
a UrlBasedViewResolver sub-class. UrlBasedViewResolver is provided
by spring-webmvc. Previously, if a user configured a web application
but did not have spring-webmvc on the classpath, the application
would fail to start with a NoClassDefFoundError for
UrlBasedViewResolver.

This commit makes GroovyWebConfiguration conditional on
UrlBasedViewResolver being on the classpath so that it backs of in
the absence of spring-webmvc.

Fixes gh-1793

Closes gh-1787

Closes gh-1774

Closes gh-1782

Fixes gh-1753

Closes gh-1708

Closes gh-1742

Closes gh-1740

Previously, there was a timing window where the output file had been
created but it was empty. This would cause the test to fail as the
output was read from the empty file and didn’t match the expected “Hello
World”.

This commit updates the test to only process the resources in the output
directory when all the resolved resources have a non-zero content
length. An @Before method has also been added to delete the output
produced by the test so that the outcome of the test isn’t affected by
files generated by previous runs.

Fixes gh-1735

Maven is configured to run tests found in classes ending in Tests.
This meant that the tests in BasicErrorControllerIntegrationTest (note
the missing s) were not being run.

This commit renames the test class so that it's picked up by Maven.

Closes gh-1710

This reverts commit 26a528ce.

Fixes gh-1706

Fixes gh-1693

Update `Launcher` and `JarFile` to correctly deal with Windows UNC
paths.

Fixes gh-1641

When logging.level.* is set in external configuration they can now
contain placeholders.

Fixes gh-1680

Closes gh-1671

Closes gh-1660

(Cherry picked from commit bebbe92f)
Fixes gh-1633

Closes gh-1474

In addition to requiring the Servlet API to be on the classpath,
MetricFilter requires spring-web to also be on the classpath as it
extends OncePerRequestFilter. This commit updates the auto-configuration
for MetricFilter so that it will be disabled in the absence of a 
dependency on spring-web.

Fixes gh-1664

Some weird looking test failures led me to track this down.
If the user changes the prefix for metric names, he probably wanted
to change the keys as welll (otherwise 2 repositories can use the
same key, which is why the test was failing for me). We can do that
in an afterPropertiesSet().

Previously, the Gradle plugin’s ProjectLibraries produced a new library
for every file dependency, even if the dependencies where on the same
file. This would lead to a repackaging failure due to multiple
libraries having the same name.

This commit updates ProjectLibraries to treat file dependencies on the
same file as a single library, thereby resolving the name clash.

Fixes gh-1646

See gh-1631