Readable tuple unpacking
Autofocus first field in new badge form
Manage instance-only badges in instance settings only

Previously, badges from other instances could be managed within the
instance settings of another instance or from the global settings. This
would lead to very long lists in the category parent chooser if
implemented properly and isn't intuitive anyway.
Refactor Badge.get_key in order to make it reusable
Fix hierarchical category creation UI

* Use flat list with hierarchy breadcrumbs instead of optgroups, which
don't work in multi-level hierarchies.
* Group parent categories by global / local instance.
Improve description of select_child_description field