Changing GUI checklist to have checkboxes instead of toggled buttons

[clockwinder]

1551-1552 - Changes buttons to have checkboxes, but retains inversion color scheme to show what options were previously selected. 1561 - Adds button borders to the bottom row

Minor documentation added

[AveYo]

Thank you for your contribution!
But as a compromise, I will go with something like this:
Don't let this discourage you!