replace single instance solution with QLocalServer
replace single instance solution with QLocalServer

a crashed instance leaves the QSharedMemory intact and so no new instances can be started

BOSSoNe0013/track-o-bot,bencart/track-o-bot,elzoido/track-o-bot,BOSSoNe0013/track-o-bot,bencart/track-o-bot,stevschmid/track-o-bot,elzoido/track-o-bot,stevschmid/track-o-bot,elzoido/track-o-bot,bencart/track-o-bot