Add `data` parameter to render_def

This adds the possibility to use Pyramid style context passing in render_def as
it has been allowed and recommended to do in render for a while.
Refactor badge index views
Split badge management in instance settings (finally fixes #665)
Add single badge type view
Add / fix some badge related 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