Re-factor keyboard dictionaries to keyboard_support

Description

Refactors much of what was in the keyboard class into the keyboard_support.
Cleans unused imports from keyboard.py
Adds keyboard.py to unit tests

Related Issue

None

Motivation and Context

It's unclear and difficult to manage when importing the keyboard class changes to choice objects. Choice objects that are imported by other grammars should be in support files.

The support files are imported only twice. Once to verify validity of Python on startup and once for all grammars regardless the number of imports of the keyboard support. ButtonDict in the support file now has a clear structure for ordering updates to the dictionary. Both modifier_choice_object and button_dictionary_1 have functions that scoped variables and execution order.

How Has This Been Tested

Testing a number of commands manually. It's too large to test all keyboard keys but it should be representative and function the same as the current master.

note: any fixes with keyboard grammar does not hold modifier keys #877 would need to be carried over to this PR. considered a work in progress until the above issue is resolved.

Types of changes

[x] Docs change / refactoring / dependency upgrade
[ ] Bug fix (non-breaking change which fixes an issue or bug)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[ ] Renamed existing command phrases (we discourage this without a strong rationale).

Checklist

[x] I have checked for and utilized existing command phrases from within Caster (delete if not applicable).
[x] I have added tests to cover my changes.
[ ] All new and existing tests pass.

Maintainer/Reviewer Checklist

[x] Basic functionality has been tested and works as claimed.
[ ] New documentation is clear and complete.
[x] Code is clear and readable.

@kendonB I noticed a keyboard grammar can conflict with the following commands. Perhaps the keyboard grammar should be adapted to replace these commands nav.py

        "<button_dictionary_500_no_prefix_no_modifier> [<nnavi500>]":
            R(Key("%(button_dictionary_500_no_prefix_no_modifier)s")*Repeat(extra='nnavi500'),
              rdescript="press buttons from button_dictionary_500_no_prefix_no_modifier"),
        "<modifier> <button_dictionary_500_modifier> [<nnavi500>]":
            R(Key("%(modifier)s%(button_dictionary_500_modifier)s")*Repeat(extra='nnavi500'),
              rdescript="press modifiers plus buttons from button_dictionary_500_modifier"),
        "<modifier> <button_dictionary_1_modifier>":
            R(Key("%(modifier)s%(button_dictionary_1_modifier)s"),
              rdescript="press modifiers plus buttons from button_dictionary_1_modifier"),

dictation-toolbox / Caster