Editor: Instance editing mode - move sub mode
Move selected instance with primary/secondary edit drags. See the tooltip of the move sub-mode for details.
Drag originating on one of the selected instances should move the objects along the plane perpendicular to the camera viewing direction. Scroll wheel movement during a drag should move the instances along the viewing direction.
Additionally while in move mode selected instances should have a marker rendered on top of them (see red/green/blue arrows in screenshot, taken from blender). The arrows should be aligned to the global coordinate system. Drags that originate on one of the markers should move the instances along the axis defined by this marker exclusively.
Note: This task requires a properly working camera to be implemented first.
(RM-3165 from redmine: created on 2016-01-26 by Marc Zinnschlag, , closed on 2016-03-12 by Marc Zinnschlag, relates #3000 (closed), relates #3245 (closed))