Refactor drag-to-move out of MoveTool and into BoxHandle.

This is a bit icky - PendingImportNode emits a signal that MoveTool handles by moving the "current import", instead of by moving the PendingImportNode's import.

TODO: Give CloneTool the same treatment.

src/mcedit2/editortools/move.py

@@ -354,9 +354,7 @@ class MoveTool(EditorTool):
 
     def toolInactive(self):
         self.editorSession.selectionTool.hideSelectionWalls = False
-
-        for node in self.pendingImportNodes.itervalues():
-            node.hoverFace(None)
+        # hide hovers for box handles?
 
     def confirmImport(self):
         if self.currentImport is None: