A hierarchy of argparse parsers.

Each parser corresponds to a command-line scope (e.g., 'compile.java').

See the code for copious comments.

Note: A future change will contain comprehensive tests for this code's
functionality.
Use JvmFingerprintStrategy in cache manager

JvmFingerprintStrategy was not used for the cache manager, causing the valid analysis file to be emptied the second time a compile was executed.

Testing Done:
Added a basic java compile integration test. Calls pants compile on a java test project twice, checking that the analysis file is valid each time.

Reviewed at https://rbcommons.com/s/twitter/r/835/
Update front-facing help and error messages for Android targets/tasks

Small improvements to an exception message and a CLI flag.
The missing manifest error in android_target didn't give
any hints as to where the bad BUILD file entry was pointing.

And the sdk-path CLI flag for android_task wasn't clear about what it did.
It could easily have been interpreted as forcing a platform
version (i.e. SDK platform 17) as opposed to what it
actually is meant to do, which is point to an entire
Android SDK installation somewhere on the filesystem.

The use case is to force a custom SDK over the AOSP one on
the machines path. Lots of OEM customize the framework and
might have multiple SDKs on the fs.

Testing Done:
CI passes.

Travis passes [0].

[0] https://travis-ci.org/pantsbuild/pants/builds/31784570

Reviewed at https://rbcommons.com/s/twitter/r/837/
Rename pants.goal.goal.Goal to pants.goal.task_registrar.TaskRegistrar.

Rename pants.command.goal.Goal to pants.command.goal_runner.GoalRunner.

There is now no class called Goal, no file called goal.py and no target called :goal anywhere.
Add assert_list to ensure an argument is a list

Testing Done:
Ran unit tests locally

Reviewed at https://rbcommons.com/s/twitter/r/811/
Updates error message when referencing the wrong path to a BUILD file.

Before, it would just spit out the incorrect BUILD file path.:

  Exception message: BUILD file does not exist at: /Users/zundel/Src/Pants/src/java/com/pants/examples/annotation/exampleTYPO

Now it will read as follows:

  Exception message: BUILD file does not exist at: /Users/zundel/Src/Pants/src/java/com/pants/examples/annotation/exampleTYPO
    referenced from src/java/com/pants/examples/annotation/processor:processor
    referenced from src/java/com/pants/examples/annotation/main:main

Testing Done:
Updated unit tests, ci passed at https://travis-ci.org/pantsbuild/pants/jobs/31812266

Bugs closed: 442

Reviewed at https://rbcommons.com/s/twitter/r/841/
Properly order resources for pants goal test and pants goal run.

Fixed a problem with goal run and test for resources being put on the classpath in the
wrong order when multiple resource paths contain the same resource path.

Added a project with resources that collide and an integration test to prove
that resources are bundled and added to the classpath in the right order.

Note that the JVM tests will still fail if all run together with

   pants goal test maven_src/resource_collision::

because pants runs all the tests in the same junit test runner instance.