#10 Add settings menu

The overflow menu is becoming quite clogged. To only list things in it that are intended for frequent use and not settings, a settings menu should be implemented. It could look like the following, replacing the corresponding menu items.

## View

[ ] Parse to table
(↓) Parser
[ ] Filter
[↓] Set filters

## Login

___ ID
_*_ Pass

## Updates

(↓) Automatically check for updates
 › Never
 › Occasionally (recommended)
 › Every launch
→ Check for updates now

## About

Developed by Fynn Godau
→ Thank him via email
→ Ask for a parser to be added
→ Check out the repository
→ File an issue

I'm not so sure about the "About" part. Maybe it should be left out.

These settings should be added for "Time Travel" as outlined in #7.

## Time travel

(↓) Delete plan files older than
 › Three days
 › One week (default)
 › Two weeks
 › One month
 › Three months
 › an Eternity (only delete manually)
→ Delete all files now

Implemented with 4a3fb55126.