* Moved methods to cpp file (less recompilation)
* Background of icons can be changed
* refs #322, changed to index based approach for retrieving icons (faster)
* therfore: sorted icons per name, easier to keep in sync
* 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