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* Outdated propertyByIndexAsString methods removed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/blackgui/models/serverlistmodel.h

@@ -54,8 +54,7 @@ namespace BlackGui
             }
 
             //! \copydoc CListModelBase::data
-            virtual QVariant data(const QModelIndex &index, int role) const;
-
+            virtual QVariant data(const QModelIndex &index, int role) const override;
         };
     }
 }