Make Keyboard modifiers conform to OS X Finder and App conventions in Editor

Holding down Shift Key while drawing a marquee in the editor should toggle the selection state of all nodes the overlap the area selected. Currently as soon as one clicks in the Editor comp window while holding the Shift Key down whatever is selected is deselected before one can add or subtract from the selection of nodes.

Command Key held down while marqueeing could just select wires not the nodes… but not sure that’s hugely useful, still not a big Vuo user so probably have more opinions in time to come.

Merged with similar feature request Use conventional keyboard modifiers for changing the selection of nodes in Editor.