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.
