Sidebar cleanup and minor fixes

[vkbo]

Summary:

This PR:

• Fixes a few minor issues in the code.
• Changes the spell checker to only spell check words with only letters in them (Python str.isalpha()).
• Removes the text labels in the side bar and converts it to a layout box with tool buttons. The tool buttons have the same style sheets as other tool buttons in the app.
• Takes control over the popup location of the menu on the Settings button. It will now always pop up to the right of the button, growing upwards from the bottom of the button.

Related Issue(s):

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