Split up the base_parser function

The goal of breaking apart the base_parser() function is to get rid of
a bunch of conditionals and parameters in the code and, instead, make
code look like simple composition.

When splitting, a choice had to be made as to whether this would operate
by side effect (modifying a passed in parser) or side effect-free
(returning a new parser everytime).

Making a version that's side-effect-free appears to be fighting with the
optparse API (it wants to work by creating a parser object, configuring
the object, and then parsing the arguments with it) so instead, make it
clear that our helper functions are modifying the passed in parser by
(1) not returning the parser and (2) changing the function names to be
more clear that it is operating by side-effect.

Also move all of the generic optparse code, along with the argument
context classes, into a new subdirectory.

test/units/executor/test_task_queue_manager_callbacks.py

@@ -21,8 +21,8 @@ from __future__ import (absolute_import, division, print_function)
 from units.compat import unittest
 from units.compat.mock import MagicMock
 
-from ansible import arguments
 from ansible import context
+from ansible.arguments import context_objects as co
 from ansible.executor.task_queue_manager import TaskQueueManager
 from ansible.playbook import Playbook
 from ansible.plugins.callback import CallbackBase
@@ -38,7 +38,7 @@ class TestTaskQueueManagerCallbacks(unittest.TestCase):
         passwords = []
 
         # Reset the stored command line args
-        arguments.GlobalCLIArgs._Singleton__instance = None
+        co.GlobalCLIArgs._Singleton__instance = None
         self._tqm = TaskQueueManager(inventory, variable_manager, loader, passwords)
         self._playbook = Playbook(loader)
 
@@ -51,7 +51,7 @@ class TestTaskQueueManagerCallbacks(unittest.TestCase):
 
     def tearDown(self):
         # Reset the stored command line args
-        arguments.GlobalCLIArgs._Singleton__instance = None
+        co.GlobalCLIArgs._Singleton__instance = None
 
     def test_task_queue_manager_callbacks_v2_playbook_on_start(self):
         """