refs #319, added column formatters

* Specialized formatters (e.g. for bool, for PQs etc.) allow specialized look and feel for each column
* Fixed isValidComFrequency used for formatters
* Changed models to use formatters
* Outdated propertyByIndexAsString methods removed
* During the above tasks: fixed override keyword in some places
* Column tooltips
* refs #323, wrong column name fix

src/blackmisc/avatcstation.h

@@ -278,9 +278,6 @@ namespace BlackMisc
             //! \copydoc CValueObject::setPropertyByIndex(variant, index)
             virtual void setPropertyByIndex(const QVariant &variant, const CPropertyIndex &index) override;
 
-            //! \copydoc CValueObject::propertyByIndexAsString()
-            virtual QString propertyByIndexAsString(const BlackMisc::CPropertyIndex &index, bool i18n = false) const override;
-
             //! \copydoc CValueObject::toJson
             virtual QJsonObject toJson() const override;