Blender Git Loki

GP UI - 2D/3D Split: Move all 3D toolbar only panel code to space_view3d_toolbar.py

* All toolbar panels that are only used in the 3D view have now been
moved out of properties_gpencil_common.py, as they are *only* used
in that editor.

* Sculpt, Edit, and Eraser panel definiitions remain in the common file
for now, as it's still possible for these to be used in other editors
(at least in theory - there may be some new limitations I haven't found yet)