Make MozStumbler beautiful.

Adds icons to MozStumbler, removes Quit.
Service stops when unbound and not scanning.

Consider removing Quit menu option completely.
Changes as requested by @cpeterso.
Merge pull request #400 from tamcap/service_stop

Stop service when the app stops. (@tamcap)
Merge pull request #403 from tamcap/beautify

Add menu icons (@tamcap)