Allow full font style settings for GUI and editor

[vkbo]

Summary:

This PR enables the full usage of the font style options for the GUI and document font selection. It saves all available font settings to the config file, but since the full settings include the font size, the old setting has been removed and will be reset to default the first time the app is loaded as 2.5

Related Issue(s):

Closes #1733

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed