Blender Git Loki

Added bpy.types.ID.make_local() that can make a single ID block local.

This new `bpy.types.ID.make_local(clear_proxies=True)` allows Python
code to press the "Make Local" button on any ID block. I chose
`clear_proxies=True` as the default, since it's the default behaviour
of `id_make_local()` (defined in `library.c`).

The caller does need to take care of ensuring that linked-in objects
don't refer to local data, and that proxies aren't broken.

Reviewers: sergey, mont29

Reviewed By: mont29

Subscribers: dfelinto

Differential Revision: https://developer.blender.org/D2346