Blender Git Loki

Grease Pencil Drawing: Default to storing on the scene when painting in 3D View

Grease Pencil will now draw on scene-level when drawing in the 3D view,
unless the active object has grease pencil data assigned (i.e. for files
saved in old versions).

The per-object method proved to be far too messy and confusing in practice,
as it was often all too easy to forget which object you had painted with.

While at present, the place where it stores strokes isn't able to be configured
from the UI yet, simply hooking up a Grease Pencil datablock into an Object's
Grease Pencil data slot should work (some tweaks are coming in the following commit
to add support for this)