Blender Git Loki

Merge branch 'master' into wiggly-widgets

change widget code, area now just stores a pointer to the widget list
corresponidng to it.

Merge branch 'master' into wiggly-widgets

Widgets API.

This commit has first WIP code for widgets API.
Generally widgets should be registered similar to dropboxes, that is,
any code can query for a widgetmap for a certain space and area type
and the window manager will take care of initializing the handlers
automatically.

The owner will be able remove and readd widgets to a certain widgetmap
dynamically. Generally owners should cleanup their widgets though initial code
cleans up leftover widgets automatically.

All this is the theory still, some parts are in that commit, more to come
later, but it's a solid base to build from for an initial commit.