refs #314, fromQVariant / location of toQVariant

* 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

src/blackmisc/pqangle.cpp

@@ -9,6 +9,7 @@
 
 #include "iconlist.h"
 #include "pqangle.h"
+#include "avheading.h"
 
 namespace BlackMisc
 {