don't hide docs for exclusives= target param in an unpublished docstring.
Review Request #865 - Created Aug. 12, 2014 and submitted
A blurb about how to use exclusives was hiding in the CheckExclusives goal doc. Many BUILD dictionary entries mentioned this, but weren't high-tech enough to "hyperlink" that doc. So... move the "user-facing" exclusives doc out of tasks/check_exclusives.py into docs/build_files.rst. in many backend/.../targets/*.py files, link to the new location.
generated doc set, eyeballed to make sure my automated comment-fixup doesn't destroy the world's syntax, kicked off https://travis-ci.org/pantsbuild/pants/builds/32287735