Fix being unable to add user via admin
Fixed admin validation to be done on both adding and editing.
Just some minor cosmetic tweaks/fixes while I familiarise myself with the code.

- Make navbar static, fixed isn't necessary.
- Fixed footer exceeding window height when it is fixed to the bottom.
- Tweaked user settings' grid sizes (lots of lg usage where sm is appropriate)
- Made admin forms more consistent with user settings forms; removed 'add' forms and just used edit forms for adding stuff - they were identical files.