better photo gallery administration

All in all:

- New module to administer all galeries

- New module to display a set of galeries

- Idea: Generate the invisible menu structure far behind and make it a lot easier for the user because he doesn't have to do this and the html pages are generated automatically. Hence they cannot be edited because they are now automatically generated

- Replaces the current way and alters the menu tree if the current galeries are not made how they should be. Maybe we use a option that prevents the use of this module if it's critical for the user