Blender Git Loki

Porting of Graph Editor's UI to python, just header done for now.
Brecht, I added a Layout template function, template_dopesheet_filter -> uiTemplateDopeSheetFilter, this creates the group of buttons for filtering ID type (and some other options) for animation editors (Graph, NLA and Dopesheet). I hope this is all right, if not, we can move this maybe to a .py file as a function for reuse.