User-friendly Algernon settings

[bewee]

As an unexperienced user, I want to have a user-friendly settings UI, in order to easier understand the meaning and effect of settings.

Acceptance criteria

• Add popup for key combo selection by typing the desired key combo
• In connection with Making order of categories configurable #204: Add popup for Category prioritization
• In connection with Quick actions #205: Add popup for quick action setup
• Use these in Algernons own search results
• Add verb settings
• Keep the existing settings as backup

[FranzSw]

A different approach would be to try and extend the fields of the Preference Browser with custom fields. Might be better, because preferences and Algernon would be kept apart. Also, the preference browser persists settings (e.g. updates).