Blender Git Loki

GP Sculpt: "Clone" Brush

Added a new brush which allows you to paste copies of whatever is on the clipboard
wherever you click. If after clicking you're not yet satisfied with where you clicked,
you can move the mouse to position the new strokes in an alternative place instead.

Future Todo's:
* Check whether this works in all views (especially 2d views)
* Fix version patching

* Remove/disable the UI options for brush size/strength, which currently have no use.
Otherwise, we could experiment with allowing those to be used for a "smudging"
effect, where the strength of the repositioning effect depends on the placement
of the stroke points relative to the cursor.