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/
make it clear: you can only download those pexes because you previously uploaded 'em.

they don't appear by magic.

Reviewed at https://rbcommons.com/s/twitter/r/1296/
Ensure that the new options system reports goals in the right order.

We sometimes rely on this, e.g., when specifying "clean-all compile".

Testing Done:
option unittests pass. CI passed when run with https://rbcommons.com/s/twitter/r/1309/

Reviewed at https://rbcommons.com/s/twitter/r/1308/
Switch option parsing for goals to the new parser.

Relies on https://rbcommons.com/s/twitter/r/1308/.

Testing Done:
CI passed when run with https://rbcommons.com/s/twitter/r/1308/.

Reviewed at https://rbcommons.com/s/twitter/r/1309/