Get rid of the t.c.contextutil dep entirely.

- Cleaned up a stray use in code that got committed after my previous change.
- Also cleaned up style in that code. Will ding code-reviewer for not addressing.
- Fixed some missing deps.
Validate that junit_tests targets have non-empty sources

- Validate the sources parameter to JavaTests
- Test that nil/empty/unmatched-globs for sources are disallowed

Testing Done:
new test added for validation

Reviewed at https://rbcommons.com/s/twitter/r/619/
Followup fix for https://rbcommons.com/s/twitter/r/619/
Make the ivy utils test work. It previously didn't have a BUILD target
and so never ran.

Also add a couple of missing deps.
Also rearrange some deps alphabetically.
Followup fix for https://rbcommons.com/s/twitter/r/619/
Restore Context after mocking it for tests (fixes CI); fix dep

Testing Done:
./build-support/bin/ci.sh

Reviewed at https://rbcommons.com/s/twitter/r/731/
Fix bad dep.

Testing Done:
CI spinning here: https://travis-ci.org/pantsbuild/pants/builds/30800681

Bugs closed: 392

Reviewed at https://rbcommons.com/s/twitter/r/742/
Move code out of goal/__init__.py into goal/goal.py.

We want all our __init__.py files to be empty, and this one actually
illustrates why: the target containing __init__.py depends on phase.py,
and has that dep explicitly in the BUILD file. However you can't load
phase.py without executing __init__.py, so there's also an implicit
dep in the other direction that you can't express in the BUILD file
without causing a circular dep.
Squashed commit of the following:

commit 3ce9ca2871770bb5fc57bd81d7ebbb51e433c80c
Author: John Ioannidis <jioannidis@twitter.com>
Date:   Tue Jul 8 01:58:42 2014 -0400

    Added cobertura coverage
Merge branch 'master' of https://github.com/pantsbuild/pants
Fixup long-missing pants_exe and goal deps exposed by a cleanup of other deps.

Testing Done:
Travis CI away here: https://travis-ci.org/pantsbuild/pants/builds/30806546
Local test kept timing out on package downloads.

Bugs closed: 393

Reviewed at https://rbcommons.com/s/twitter/r/745/
Update contributors guide for rbt fixes

Account for the closed `rbt` bug in the contributors guide.

Reviewed at https://rbcommons.com/s/twitter/r/738/
fix docs about docs.

I wanted to make sure a fix to 'goal markdown' didn't break 'goal confluence'.
So I had to get 'goal confluence' working. Along the way, figured out our
instructions were wrong, d'oh

Testing Done:
published a couple of pages to a wiki.

Bugs left over: 395

Bugs closed: 385, 387

Reviewed at https://rbcommons.com/s/twitter/r/730/
missing dep

Travis-CI had a sad. This updated dep makes Travis-CI happy.

Testing Done:
https://travis-ci.org/pantsbuild/pants/builds/30852643

Reviewed at https://rbcommons.com/s/twitter/r/748/
Upgrade to twitter.common.python 0.6.0 and adjust to api change.

This came up over here: https://rbcommons.com/s/twitter/r/737/

Testing Done:
$ ./build-support/bin/ci.sh

Bugs closed: 394

Reviewed at https://rbcommons.com/s/twitter/r/746/
First attempt for issue https://github.com/pantsbuild/pants/issues/326

End pants users arguably see no values from the stack trace (even if they occasionally do, they can use the reporting server log); but in PANTS_DEV mode, pants dev should see the stack. The change is to introduce a command line arg that pants bash script will pass to pants_exe if PANTS_DEV is set. And in pants_exe we setup an unhandled exception hook to print out the exception's stacktrace plus msg based on the cmdline arg's presence.

Testing Done:
17:04:04 05:01     [specs]
               Waiting for background workers to finish.
               SUCCESS
$ ./pants goal test tests::

Bugs closed: 326

Reviewed at https://rbcommons.com/s/twitter/r/655/
Get rid of code in scm/__init__.py.

Having code in __init__.py is bad practice in pants-world, due to possible
dependency issues: __init__.py is always executed when any code in a package
is loaded, even if that code has no visible import dependency on __init__.py,
and therefore no BUILD file dependency on it.
Get rid of code in distribution/__init__.py.
Remove last non-empty __init__.py file.

We no longer have namespace issues with tests/python/pants_test.
Restore namespace package to src/python/pants/__init__.py.

It turns out to be needed after all.

This reverts the salient part of commit 583eed04142a0aaa9afd525c178b834373f5ef22.