Action/ToggleAction classes moved into their own module. The

actions.__init__ module contains aliases for all the global Action
classes. FSLEyesFrame no longer stores a dict of {AuiPaneInfo :
ViewPanel} mappings, because AuiPaneInfo objects are evidently not
persistent, so I cannot use them as dict keys. New action -
ClearPerspectiveAction, which delets all user-saved
perspectives. SavePerspectiveAction is functional.  Perspectives module
is functional, but needs more work w.r.t. managing built-in
perspectives.