Add setLocation() and getLocation() methods for ActionMgr.
Add some pretty-printing code to display the "Shell Command" action's
command name within the action Oval. Only shows the command's based name
(e.g. "gcc-4.7").
Implement "move" functionality for UIAction pictograms on a package
diagram. Undo/redo also works, although the package diagram doesn't yet
correctly redraw.