ENH: Allow disabling slice view interactions

For interventional applications it is often necessary to prevent the user from manipulating a slice view (change selected slice, adjust window width/level, etc).

SetActionEnabled/GetActionEnabled methods have been added to specify which actions are allowed in a slice view (default behavior is the same as before: all actions are allowed).

Example:
interactorStyle = slicer.app.layoutManager().sliceWidget('Red').sliceView().sliceViewInteractorStyle()
interactorStyle.SetActionEnabled(interactorStyle.BrowseSlice, False)

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25997 3bd1e089-480b-0410-8dfb-8563597acbee