* renamed fromQVariant to convertFromQVariant, the "from" methods imply the object is changed (fromJson, fromString ..)
* implemented fromQVariant - changing the object by QVariant
* moved toQVariant into PQ template
* free function setFromQVariant
* changed return type for updateFromVatsimDataFileStation
* improved resolution for own aircraft
* convenience method findFirstByCallsign
* automatically convert frequency to MHz for ATC station
* improved output in toQString
* GUI, flight plan formatting
* corrected logging for network context
* override keyword in listmodelbase