View2D: Scroller Manipulations

View2D: Scroller Manipulations

Implemented operator to work with scrollers. This should work reasonably well, but as always, more testing is needed.
* LMB-drag can now be used to initiate manipulations of scrollbars (so they can be dragged as per normal)
* By clicking on the 'dark regions' on the ends of the scroll bubble, it is possible to zoom the view (in a way similar to Sony Vegas scrollbars)

Tidied up code of other operators
* Re-labelled the current zoom operators, as there is still a modal click-drag zoom tool to be ported still
* Marked all of the existing view manipulation operators as redoable. Scrollers manipulator is not allowed to be redoable.

Assorted changes:
* Added more flags for Outliner on reading old files, to prevent more weird things happening as code expects certain flags these days