Rename KeyBindingMode to ActionMode

The keybinding mode is no longer used exclusively for actions triggered
by keybindings, so reflect this by a more generic name.

https://bugzilla.gnome.org/show_bug.cgi?id=740237

js/ui/unlockDialog.js

@@ -154,7 +154,7 @@ const UnlockDialog = new Lang.Class({
             return true;
 
         if (!Main.pushModal(this.actor, { timestamp: timestamp,
-                                          keybindingMode: Shell.KeyBindingMode.UNLOCK_SCREEN }))
+                                          actionMode: Shell.ActionMode.UNLOCK_SCREEN }))
             return false;
 
         this._isModal = true;