Blender Git Loki

View2D: Modal Ctrl-MMB-drag Zoom Restored

Added back the Ctrl-MMB-drag zoom.
* It uses RNA-props for delta amounts to be added to the cur rect, as opposed to storing a transform factor like the others.
* Made the operator another repeatable one
* The user-pref Continue/Dolly/Scale options are still respected. Currently, this is not stored as an RNA-prop for repeated behaviour, as it is not necessary for this operator to function correctly (and also, this data would fall under 'context' info more)

Removed clamping of scroller 'bubble' to bounds of scroller, as it produced a confusing display when using handles to zoom view.