Relativize classpath for non-ng java execution

-Factored the classpath relativization logic into it's own module and reworked it slightly.
-Made jmake relativize classpath in addition to the nailgun executor

The jvm_utils BUILD file has an empty dependencies key to follow the convention I found in another file.

Testing Done:
Ran a java/scala test target with nailgun enabled/disabled and made sure the classpath was minimized and the tests passed.

Reviewed at https://rbcommons.com/s/twitter/r/804/
Fixup JvmCompile to always deliver non-None products that were required by downstream.

This change augments GroupTask with a pre_execute complement to post_execute and
uses this lifecycle point to ensure JvmCompile delivers on its promise of supply product maps
regardless of the availability of chunks in the round.  Further adds tests for the new lifecycle
as well as coverage for pre-existing un-tested always-run semantics of construct, prepare and
post-execute.

Testing Done:
Travis CI went green here: https://travis-ci.org/pantsbuild/pants/builds/31199740

Also:
==
$ PANTS_DEV=1 ./pants goal test tests/python/pants_test/tasks/:group_task --test-pytest-options=-v
...
21:12:20 00:01   [test]
21:12:20 00:01     [pytest]
21:12:20 00:01       [run]
                     ============== test session starts ===============
                     platform linux2 -- Python 2.6.9 -- py-1.4.22 -- pytest-2.6.0 -- /usr/bin/python2.6
                     plugins: cov, timeout
                     collected 5 items

                     tests/python/pants_test/tasks/test_group_task.py@57::GroupIteratorSingleTest::test PASSED
                     tests/python/pants_test/tasks/test_group_task.py@73::GroupIteratorMultipleTest::test PASSED
                     tests/python/pants_test/tasks/test_group_task.py@179::GroupTaskTest::test_groups PASSED
                     tests/python/pants_test/tasks/test_group_task.py@232::EmptyGroupTaskTest::test_groups PASSED
                     tests/python/pants_test/tasks/test_group_task.py@263::TransitiveGroupTaskTest::test_transitive_groups PASSED

                     ============ 5 passed in 0.17 seconds ============

And tested this change live against an internal use-case that was failing before this as such:
==
...
  File "/Users/david/.pex/install/pantsbuild.pants-0.0.21-py2-none-any.whl.0ce746980853d744737145525a44d8f91b0c5d84/pantsbuild.pants-0.0.21-py2-none-any.whl/pants/engine/round_engine.py", line 42, in attempt
    task.execute()
  File "/Users/david/.pex/install/twitter.common.pants-0.4.0-py2-none-any.whl.e1f378c90f5282b48c1ebc94c79373050751b771/twitter.common.pants-0.4.0-py2-none-any.whl/twitter/common/pants/jvm/args/tasks/resource_mapper.py", line 99, in execute
    self._add_args_resources(target, resources_by_target, transitive=False)
  File "/Users/david/.pex/install/twitter.common.pants-0.4.0-py2-none-any.whl.e1f378c90f5282b48c1ebc94c79373050751b771/twitter.common.pants-0.4.0-py2-none-any.whl/twitter/common/pants/jvm/args/tasks/resource_mapper.py", line 118, in _add_args_resources
    collect_resource_dirs(target)
  File "/Users/david/.pex/install/twitter.common.pants-0.4.0-py2-none-any.whl.e1f378c90f5282b48c1ebc94c79373050751b771/twitter.common.pants-0.4.0-py2-none-any.whl/twitter/common/pants/jvm/args/tasks/resource_mapper.py", line 110, in collect_resource_dirs
    mapping = classes_by_target.get(tgt)
AttributeError: 'NoneType' object has no attribute 'get'

Notably, this is the t.c.pants args-apt plugin [1] and it requires 'classes_by_target' [2], but gets None [3] prior to this fix.
[1] https://pypi.python.org/pypi/twitter.common.pants/0.4.0
[2] https://github.com/twitter/commons/blob/master/pants-plugins/src/python/twitter/common/pants/jvm/args/tasks/resource_mapper.py#L89
[3] https://github.com/twitter/commons/blob/master/pants-plugins/src/python/twitter/common/pants/jvm/args/tasks/resource_mapper.py#L105

Bugs closed: 415

Reviewed at https://rbcommons.com/s/twitter/r/794/
Create a mixin for "quiet tasks".

This separates the two concerns formerly handled by ConsoleTask:
being quiet, and being a task whose primary job is to print to the console.

Now you mix in QuietTaskMixin for the first, and extend ConsoleTask
(which itself mixes in QuietTaskMixin) for the second.

This rids us of silliness such as the clean-all task having a flag
to specify its output separator.
`goal repl` consumes targets transitively

- Partition by selected language vs all other languages to allow for handling of 'dependencies'/'jar_library' and other inner nodes
- Filter the entire context, rather than just target roots
- Label JarLibrary as a JVM target (and fix related fallout)

Testing Done:
new unit test
manual validation of mixed/scala/python contexts:

-----
PANTS_DEV=1 ./pants goal repl src/scala/com/pants/testproject/unicode
...
scala> com.pants.testproject.unicode.shapeless.ShapelessExample.greek()
res1: String = shapeless success
-----
PANTS_DEV=1 ./pants goal repl src/python/example/hello/greet
...
>>> from example.hello.greet.greet import greet
>>> greet("yo")
u'\x1b[32mHello, yo!\x1b[0m'
-----
PANTS_DEV=1 ./pants goal repl src/scala/com/pants/testproject/unicode src/python/example/hello/greet
...
FAILURE: Mutually incompatible targets specified: PythonLibrary(BuildFileAddress(/Users/stuhood/src/pants/src/python/example/hello/greet/BUILD, greet)) vs ScalaLibrary(BuildFileAddress(/Users/stuhood/src/pants/src/scala/com/pants/testproject/unicode/shapeless/BUILD, shapeless))
-----

Reviewed at https://rbcommons.com/s/twitter/r/781/
Merge remote-tracking branch 'origin/master' into jco/list_validation