simplified skin changing

[berni03]

If you install a new skin you have to search and copy all your plugin-specific xml and image files from your previous skin's folder to your new skin's folder, which is a time consuming task if you use a lot of plugins.

A solution to this would be something like a skin/common/ folder where plugin specific xmls and images could be stored.
If a file is not found in the skin's folder it should be searched in this folder before showing the missing/invalid file error.

This would
- allow users to change skins without having to worry about plugin-specific files and would
- allow plugin developers to distribute there plugins in self-extracting packages since the location of the plugin-specific files relative to the mp directory would be fixed (e.g in /skin/common/) instead of requiring the users to put them in their skin's folder.

I think this would improve the usuability of mp and would make mp easier to understand for new users.
please tell me what you think about this idea and how it could be improved