Blender Git Loki

NLA: Always Show All Strips

Currently, it's difficult to use the NLA system for users who are only
interested in using it as animation layers.

Entering tweak mode hides strips which are not evaluated. If the user
wanted to edit a different strip, they must exit tweak mode, look for
the strip, select it then re-enter tweak mode.

Solution:
All strips are always shown. The user can now see the next strip they
want to start editing.

Reviewed By: Sybren, Sebastian Parborg

Differential Revision: https://developer.blender.org/D7600