Fix the bbox attributes

The current inkscape patch update the bbox in the cuurent level only. It does not update the bbox of the included elements. We need to be very careful to fix it. We should modify the code to update all existing bbox attributes in a group when we change it.

Add scene support

Support the original python plugin and support it in the javascript framework.

Warn users the MB object is deleted

Warning users when we want to delete elements with inkscape:label. This can prevent the art designer to delete objects which is used by the programmer.

Object name editor

Add the object name and type editor to assign the inkscape:label and mbtype field. In addition, we will display different options for different mbtype. For example, for button type, we will display a combo box which can be used to switch between normal/press/release mode.

Preview

Execute the specified js file to see the result. Art designer can use this function to preview their modification in the real program. We should generate useful report to tell the art designer when there is any missing objects, which need to be defined in the scene.