Show cmd line info on 'gradle help --task <task>'

Info is shown when invoking 'gradle tasks' on the cmd line.

+review REVIEW-5256
Fix documented path

+review REVIEW-5256
Adjust output

Help on 'gradle help --task <task>' is shown when invoking 'gradle tasks' on the cmd line.

+review REVIEW-5256
GRADLE-3147: Only exclude module if artifact name, type or ext attributes are not specified. Otherwise, filter artifacts of a module based on exclusion expression. Transitive diamond exclude for single path doesn't work properly yet.
let Play ToolChain choose TwirlCompiler version based on provided PlayPlatform

+review REVIEW-5258
Respect forkoptions when forking twirl compiler

+review REVIEW-5258
GRADLE-3147: Removed redundancy in test cases.
GRADLE-3147: Renamed ArtifactIdSpec to ArtifactVersionSpec to align with naming we have in place for ModuleVersionSpec.
Update RoutesCompileIntegrationTest.groovy
allow only one target play version for a play component

- make forking default for twirlcompile without option to disable atm
+review REVIEW-5241
Fail if more than one PlayApplicationSpec is registered

+review REVIEW-5241
fork scala compiler per default in play applications

+review REVIEW-5246
let PlatformAwareComponentSpec extend ComponentSpec
Fix testListener sample.

It was broken for a long time due to rename of property in Test (0.9)
and build classpath change (2.0).
Simplified sample.
Removed duplicate int test
Simplified dealing with `colorOutput` property in the tooling api provider.
Changed ProtocolToModelAdapter to handle `is` methods the same way as `get` methods.
Removed filtering for message that is no longer generated.
Reuse `RedirectStdOutAndErr` rule and removed copy.