Refactor the Cotton Candy front-end onto Bootstrap

[bartfeenstra]

This fixes #908
This fixes #717

[github-actions]

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[github-actions]

🪟 Uploaded betty.exe.zip for commit cafba21. You can download it, test it on Windows, and post your feedback in a comment to this pull request 💕

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b4f2e3d) 92.93% compared to head (f90ca8e) 92.95%.
Report is 163 commits behind head on 0.3.x.

Additional details and impacted files

@@            Coverage Diff             @@
##            0.3.x    #1003      +/-   ##
==========================================
+ Coverage   92.93%   92.95%   +0.02%     
==========================================
  Files          75       75              
  Lines        8052     8053       +1     
==========================================
+ Hits         7483     7486       +3     
+ Misses        569      567       -2     

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[github-actions]

🍎 Uploaded betty.app.zip for commit 83bb11d. You can download it, test it on Mac OS, and post your feedback in a comment to this pull request 💕

The download will disappear once this pull request is merged, or when it is being rebuilt after a new commit.

[github-actions]

🪟 Uploaded betty.exe.zip for commit 83bb11d. You can download it, test it on Windows, and post your feedback in a comment to this pull request 💕

The download will disappear once this pull request is merged, or when it is being rebuilt after a new commit.