We should not use subprojects to perform configuration becaause it
does not allow for lazy loading and it can cause ordering problems.
In this case, the toolchain was not being used but instead it was
using the JAVA_HOME.
By splitting the configuration into a plugin and applying it to each
project it fixes the toolchain configuration
As of Spring 4.3 RC1 the `org.aopalliance` interfaces are once again bundled
with `spring-aop` [1]. Moreover, all modules with a dependency on
`aopalliance:aopalliance` directly or indirectly also depend on `spring-aop`.
This change drops the `aopalliance:aopalliance` dependency in all places it's
declared. Where applicable an explicit dependency on `spring-aop` was added in
its place. (This dependency was already present in most places; in one case the
module didn't require `aopalliance:aopalliance` in the first place.)
The documentation is updated accordingly.
[1] https://jira.spring.io/browse/SPR-13984
Robert Winch