Blender Git Loki

GP Sculpt: Added timer which can be used to "accumulate" the brush effects if held

* This is currently only used for the "twist" brush. It is useful for making points
rotate around the pivot point without needing to make constant movements to trigger
updates (whcih is undesirable here, as that would alter the transforms).

* Currently this uses a hardcoded "rate" (i.e. repeat frequency). This will be addressed
alongside other issues, such as extending this to other appropriate brush types.