Remove color from badge overview

The color is already visible in the badge preview and the table is too
big, so this can be safely removed.
Add `data` parameter to render_def
Refactor badge index
Split badge management in instance settings (finally fixes #665)
Add single badge type view
Add / fix some format parameters
Add trivial current_url helper function
Add action urls to badge related forms

As the overlay related ajax_submit javascript code requires action
attributes in the respective forms, we add these, pointing to the
current URL.
Add badge management overlays in context