Add support to filter by group

[askvortsov1]

Fixes #10

Changelog:

• Added GroupIDGambit, as otherwise we can't support groups with spaces in the name
• Added logic and UI for group filtering (using group ID gambit)

Demo Video:
https://youtu.be/tIkyLAFA8cE

[askvortsov1]

I'm considering expanding this so that stuff like #5 (the filter by suspend especially) could be added; we'd have dividers in between groups of buttons, the first group would be for groups, and others, like suspended status, could be added

[clarkwinkelmann]

I think it would be more logical to add the gambit to core, and only the controls to User Directory

[clarkwinkelmann]

@askvortsov1 are you interested in updating this to use the new native group gambit?

Maybe you'll want to create a new PR for that. Feel free to close this one.

[askvortsov1]

Updated

[imorland]

Checked out locally, appears to be as intended 👍

Thanks @askvortsov1