Remove some stray calls to setup_parser.

One is in help.py which is completely unused, so now deleted.

The other was in the new help printer.

Testing Done:
Verified that --help works.

CI passed.

Reviewed at https://rbcommons.com/s/twitter/r/1300/
docs: mention mvn2pants

while I was in there: setup_repo had a paragraph about top-dir BUILD files for config. LOL, nowadays, that config has moved into plugins. So pull that out, and re-jigger examples of BUILD.foo files.

Reviewed at https://rbcommons.com/s/twitter/r/1301/
Remove a superfluous test.

It only tests that Goal.parse_args works, but that function is
about to be killed itself.

Reviewed at https://rbcommons.com/s/twitter/r/1304/
Move cache logging to debug

Can get a tad noisy with several tasks all using setting up multiple caches.

Testing Done: https://travis-ci.org/pantsbuild/pants/builds/40392152

Bugs closed: 783

Reviewed at https://rbcommons.com/s/twitter/r/1310/