Blender Git Loki

=== Better support for user defined modal keymaps ===

Fixing/Missing RNA properties:
- "virtual" property for "ANY" modifier for keymapitem
- modal property for keymap
- Look up modal_items in usermaps too

Lazy init usermaps needs to init modal_items too.

New function to initialize a user keymap (fill in modal_item and poll pointers).

Operator modal keymaps now look up if there's a user defined keymap that overwrites it.

Full Event UI buttons now show "Any" when modifier is set to that (instead of listing all of them).

Note: Having the modifiers as boolean still doesn't express the full breath of values possible for them. There is commented code in this commit to represent them as enum, which would solve this, but make the keymap editor more cryptic.