Include spring-aspects in Spring Data JPA starter.

Declared spring-aspects as additional dependency in Spring Data JPA
starter pom. This is necessary to let the auditing feature work
correctly.
Change package name in sample
Add javadocs to some Metrics interfaces

Fixes gh-250
Document JSP limitations with executable JAR or WAR
Updates to redis repositories

* Ensure prefix ends with period
* Allow prefix and key index to be set separately
Fix type mentioned in javadocs
Don't mask original exception in SpringApplication.handleError

If any @Import (or @Enable*, especially @EnableScheduling) has registered
bean *names* as ApplicationListeners, and the application context wasn't
refreshed fully when it failed, then the listener lookup could fail and
mask the original exception

Fixes gh-253
Extend semantics of ConfigFileApplicationListener environment a bit

spring.config.[name,location] can both be a comma-separated list now. Highest
priority is last, like a hash overriding its keys (as per other conventions
in the listener).

Fixes gh-261
Add spring.messages.encoding (default utf-8)

Fixes gh-260
Polish
Refine ConfigFileApplicationListener a little
Add layout docs to plugin READMEs
Add thymeleaf starter

Fixes gh-264
Add some more smarts around --debug

--verbose seems to be only for CLI logging (so really only
for dependency resolution). --debug is interpreted by SpringApplication
but up to now has been extracted and deleted from the command line
by the CommandRunner. This change makes --debug set a System property
*and* pass it down to the application (if used with -- separator).

Fixes gh-266
Add destroyMethods to DataSources
Allow gradle builds without version numbers

Add a gradle `ResolutionStrategy` that resolves missing version numbers
using the `spring-boot-dependencies` POM.

This commit also introduces a new `spring-boot-dependency-tools` module
that provides programmatic access to the `dependencyManagement` section
of the dependencies POM.

Fixed gh-262
Update CLI to use spring-boot-dependency-tools

Update `GroovyCompiler` and `AetherGrapeEngineFactory` to use the
recently added `spring-boot-dependency-tools` in favor of loading
dependency information from a generated properties file.