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/aviocomsystem.h

@@ -39,9 +39,6 @@ namespace BlackMisc
                 CModulator(name, activeFrequency, standbyFrequency == CModulator::FrequencyNotSet() ? activeFrequency : standbyFrequency, digits), m_channelSpacing(ChannelSpacing25KHz)
             { }
 
-            //! \copydoc CValueObject::toQVariant
-            virtual QVariant toQVariant() const override { return QVariant::fromValue(*this); }
-
             //! Set active frequency
             //! \remarks will be rounded to channel spacing
             void setFrequencyActiveMHz(double frequencyMHz);