- fixed: forgot to add a "no key" option to the radiogroup from previous commits
- made that radiogroup vertical again
- started using XUL's preferences system
using XUL's preferences system for a bunch of preferences
replaced strange looking opacity slider with a textbox with spin buttons + using XUL's preferences system for this control
using XUL's preferences system for 4 additional preferences
two controls that could be hidden can now be disabled instead