[Build] Added the ability to mark tests as @Category(Slow.class) to enable faster local builds.
[Build] Changed the way we load cglib-nodep as this was generating warnings on the build, and moved proxy-toys from provided to compile, as this library usually fails to load correctly in IntelliJ
[Build] Upgraded gradle, and the various changes that forced - a welcome upgrade to Spock on the build code; an update to code from a bug found via the new version of Findbugs.