more fixes on buildSetup
- REVIEW-1997: always generate Wrapper
- REVIEW-2059: tweak task descriptions of buildSetup related tasks
- dont set group for build script and settings generator tasks (shouldnt been listed in task overview)
- rename wrapper Wrapper task to setupWrapper (don't clash with existing wrapper tasks)
REVIEW-2058 respect custom build file names when checking for existing build files.
REVIEW-2050: Add spec for docs improvement.