Cleanup startup configuration

[mdoucet]

Over the years we have cleaned up some of the configuration. This PR gets rid of a lot of dead code, which created problems for users who still had old config files lying around.

The config that existed were meant to set the default values of a few parameters: TOF binning, angle offset, etc...
Those were stored in the QSettings of the application.
There is no reason to change those defaults, and that was removed a long time ago. The following dead code was left behind:

• There was a panel to change those parameters, and the hook in the .ui file was kept but hidden. This PR removes it.
• Because the hook was kept, the callback function was also kept in the main application. We removed it.
• Because the callback was kept, the unused panel code was kept too, along with a "password" panel. They are now both gone.
• The .ui files for those panels have been removed.
• There was useless layers of code to read/write and handle those parameters. We replaced all this with a dict.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.60%. Comparing base (2b5af6f) to head (fc96685).

Additional details and impacted files

@@            Coverage Diff             @@
##             next     #144      +/-   ##
==========================================
- Coverage   63.68%   63.60%   -0.08%     
==========================================
  Files         121      117       -4     
  Lines        9915     9792     -123     
==========================================
- Hits         6314     6228      -86     
+ Misses       3601     3564      -37     

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[glass-ships]

looks good! doesn't seem like it'll have any conflicts with #141