Prepare for exposing tool registration to the Python API.
- Generated tools can use their own prefix so naming collisions
won't happen between hard coded & generated tools.
- Add-on authors can use the add-on name as a prefix.
Currently the names match, renaming will happen next.
For full keymaps, ensure keymap items are lists to allow predictable
manipulation at runtime.
When calling `keymap_init_from_data` directly, allow any sequence type
to allow tools to define their keymaps as tuples.
Also added keys for toggling harden normals,
and cycling through miter types.
Still to do: add some shortcuts for affecting the
spread value for arc miters.
Ensure we use lists for keymap items and item properties.
This means scripts can access keymap definitions from other layouts,
manipulating them without sometimes encountering a tuple that needs
to be converted into a list.
bpy_extras were meant to be useful high-level helper functions for
script authors to perform common operations,
to avoid writing to verbose API's.
bpy_extras.keymap_utils contains some specialized API calls
mainly intended for Blender's own internal use.
Move keymap import export to internal API.
