[installer][host] we already stopped using a signal to control the backbutton
[installer][host] Fix tabselection and taborder on UI (modal dialogs not fixed)
[installer][host] make Yes/No Prompts behave the same way as the Errorbox. Should enable Tabbing. Might rework this back but then we'd have to use stylesheets and extra magic
[installer][host] fix WIFI setup validation
[installer][host] add simple IP validation for manual network setup
Merge pull request #28 from srmo/master

make tab selection/order work - RETEST ON ALL HOST PLATFORMS!