Minor tweaks and refactors. A half-baked collection support and several UI tweaks.
Just committing these are they are "old" changes and the current state turns out to be pretty stable.
Added the first draft of the browser window and implemented switching between it and the importer window via menu action.
Also renamed window.py to importer_window and abstracted some features into a superclass from which the browser window can also inherit. This allows an equal interface for them.
Also fixed a bug in the db_adapter.py where an old column name was used for a query.