Upgrade to com.twitter.common#jar-tool;0.1.6

This picks up a fix for moving the temporary jar file created
to it final target location when the two reside on different
filesystems.

Testing Done:
$ PANTS_DEV=1 ./pants goal binary bundle src/java/com/pants/::

Bugs closed: 193

Reviewed at https://rbcommons.com/s/twitter/r/465/
Updated build file parser error message when the same target is redefined

Testing Done:
Added a new test in test_build_file_parser.py and updated an existing one.

I tested with

PANTS_DEV=1 ./pants tests/python/pants_test/base:build_file_parser --verbose

but am currently unable to retest or run ci because of the ... untranslatable ... errors.

Bugs closed: 192

Reviewed at https://rbcommons.com/s/twitter/r/464/
Added jaxb support for pants.

jaxb_library target now exists. It takes in sources=[] for the schema file(s), and a package='...' parameter for what package to generate the output java files in. It uses the xjc compiler included in the jdk.