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.

lib/ansible/cli/doc.py

@@ -16,6 +16,7 @@ import ansible.plugins.loader as plugin_loader
 
 from ansible import constants as C
 from ansible import context
+from ansible.arguments import optparse_helpers as opt_help
 from ansible.cli import CLI
 from ansible.errors import AnsibleError, AnsibleOptionsError
 from ansible.module_utils._text import to_native
@@ -47,12 +48,12 @@ class DocCLI(CLI):
 
     def init_parser(self):
 
-        self.parser = super(DocCLI, self).init_parser(
+        super(DocCLI, self).init_parser(
             usage='usage: %prog [-l|-F|-s] [options] [-t <plugin type> ] [plugin]',
-            module_opts=True,
             desc="plugin documentation tool",
             epilog="See man pages for Ansible CLI options or website for tutorials https://docs.ansible.com"
         )
+        opt_help.add_module_options(self.parser)
 
         self.parser.add_option("-F", "--list_files", action="store_true", default=False, dest="list_files",
                                help='Show plugin names and their source files without summaries (implies --list)')
@@ -68,7 +69,6 @@ class DocCLI(CLI):
                                help='Choose which plugin type (defaults to "module"). '
                                     'Available plugin types are : {0}'.format(C.DOCUMENTABLE_PLUGINS),
                                choices=C.DOCUMENTABLE_PLUGINS)
-        return self.parser
 
     def post_process_args(self, options, args):
         if [options.all_plugins, options.json_dump, options.list_dir, options.list_files, options.show_snippet].count(True) > 1: