Blender Git Loki

GPencil: Added a new version of the "delete active frame" operator which deletes on all editable layers

This new operator will delete any GP frame it finds on the current frame, regardless
of whether it's on the active layer or not. It will only remove the frames if the
layer is editable, but otherwise, it will just go for it.

The existing operator is great for use in the panel (where it only applies to the active
frame), but it was not so good for all the other places where tools can be invoked
(e.g. D-X, or Delete) as you're typically thinking about the whole scene more holisticaly
than just caring about a particular layer.