Closes gh-6597

Closes gh-6617

Closes gh-6608

* gh-6588:
  Polish “Allow injection of StatsDClient into StatsdMetricWriter”
  Allow injection of StatsDClient into StatsdMetricWriter

Closes gh-6588

Allow an instance of StatsDClient to be injected into the StatsdMetricWriter
which is used for exporting metrics to a Statsd server. This new constructor
allows the client to be injected but does not change the default behavior of
the writer.

Closes gh-6488

Previously, the tests class and any JUnit annotations it contained were
loaded by a different class loader to JUnit. This meant that the JUnit
annotations were loaded twice and @Rule-annotated fields were not found.
This commit updates FitleredClassPathRunner to use a custom class loader
that ensures that any org.junit.* classes are only loaded by a single
class loader.

Previously, auto-configuration of the Flyway and Liquibase endpoints
would fail if there were multiple Flyway or Spring Liquibase beans
in the application context.

This commit updates them so that they are now conditional on a single
candidate.

Closes gh-6609

See gh-6527

Previously, if mvn spring-boot:run with a forked JVM was killed with 
CTRL+C, the run would be considered unsuccessful. This commits updates
the run mojo to consider a forked JVM that exists with 130 (the exit
code produced when exiting due to SIGINT which is what CTRL+C sends) to
be successful.

Closes gh-6498

Closes gh-6650

* pr/6644:
  Upgrade to Spring Security 4.1.2.RELEASE

Closes gh-6644

* pr/6540:
  Polish contribution
  Fix health endpoint security

Closes gh-6540

Commit b02aba4c has renamed `management.security.role` to
`management.security.roles`. Unfortunately, the `HealthMvcEndpoint`
was still looking at the old property.

This commit makes sure that the proper key is used and any custom
role is applied rather than an unconditional `ADMIN` role.

See gh-6540

* gh-6623:
  Use 'travis_wait' to prevent Travis CI from aborting builds

Builds use the '-q' flag to suppress most output due to a limit of 4MB
of logs on Travis CI. However, Travis will also abort builds that
don't generate any output for 10 minutes. Thus we also use the
'travis_wait' function to make sure builds aren't aborted for up to
30 minutes.

Fixes gh-6621
Closes gh-6623

* gh-6604:
  Ensure that @LiquibaseDataSource is preferred to “normal” DataSource
  Allow a DataSource to be marked as being specifically for Liquibase

Closes gh-6604

This commit allows to configure a special DataSource to be used by
Liquibase by annotating it with @LiquibaseDataSource.

Closes gh-6614

The unpack location is (largely) an implementation detail and the
Repackage Mojo was the only place where it was explicity documented.
Rather than updating the outdated location, this commit removes it
entirely to avoid encouraging people to rely on the location.

Closes gh-6624

Closes gh-6508

* pr/6556:
  Upgrade to Elasticsearch 2.3.5

Closes gh-6556

Closes gh-6628

Closes gh-6549

Call afterPropertiesSet on the delegate `ResourceHttpRequestHandler`
to prevent an NPE. This change is required for compatibility with
Spring Framework 4.3 following SPR-13834.

Closes gh-6592

Previously, CLI extensions where installed into the CLI's lib
directory which meant that they were on the class path of the app
class loader. Following the change to an executable jar's packaging,
this meant that they could not see classes in the CLI and a
ClassNotFoundException would result.

This commit updates the CLI to install extensions into lib/ext and
load commands using a new ClassLoader that has all of the jars in
lib/ext on its class path and that uses the launch class loader as
its parent.

Closes gh-6615

Previously, if a single FailureAnalyzer failed to load, no failure
analysis would be performed. This commit updates FailureAnalyzers to
load the analysers defensively so that all but the problematic analyzer
are used for analysis.

Closes gh-6606

Previously, MetricExportAutoConfiguration consumed
ExportMetricWriter-annotated GaugeWriter beans in its constructor and
also produced such a bean from one of its @Bean methods. This cycle
caused a BeanCurrentlyInCreationException to be thrown when the
bean method was active (the spring.metrics.export.statsd.host property
was set).

This commit break the cycle by moving the bean method into a separate,
nested configuration class. It also updates the existing test for
auto-configuration of a Statsd writer to catch any possible cycles
and to verify that the writer has be registered with the
MetricsExporter.

Closes gh-6544

META-INF/INDEX.LIST files are pointless in an executable jar and
moving application classes from the root of the jar to
BOOT-INF/classes breaks the index, resulting in an
InvalidJarIndexException being thrown.

This commit updates the Repackager to automatically remove a
META-INF/INDEX.LIST file from a jar file that is being repackaged.

Closes gh-6601