refactor: use progress_bar more explicitly as a thread

[aron-bram]

I did not like the way the progress bar class started itself as soon as it was instatiated, so I changed the way it works to be more intuitive. Namely, ProgressBar can now be used just like a regular thread, so start() has to be called on it for it to start running. Also, join is used to wait for it to finish, which at the same time terminates the thread by maxing out the bar, so that the thread will never hang.

I also added improved docs.

[codecov]

Codecov Report

Merging #1622 (318cfd2) into development (1abd1f9) will decrease coverage by 0.14%.
The diff coverage is 90.00%.

Additional details and impacted files

@@               Coverage Diff               @@
##           development    #1622      +/-   ##
===============================================
- Coverage        83.42%   83.27%   -0.15%     
===============================================
  Files              156      156              
  Lines            11927    11931       +4     
  Branches          1896     1897       +1     
===============================================
- Hits              9950     9936      -14     
- Misses            1412     1425      +13     
- Partials           565      570       +5     

[eddiebergman]

Looks good, I'll leave the documentation part up to you to decide if you want to fix it, otherwise feel free to merge it yourself!

Make sure to use the Squash and Merge option when merging, it should show on the button if not already.