Wizards: add IconListField

- reuse some code from ComboBoxField throw an abstract ListField class
 - ListField can handle more data like: icon, trToolTip
 - fix disabledIndex in ComboBoxField
 - adjust documentation

Change-Id: I00b6ab787fb2fad97dafff32786cf73c636c772d
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/jsonwizard/jsonfieldpage.h

@@ -42,7 +42,6 @@ QT_END_NAMESPACE
 
 namespace Utils {
 class MacroExpander;
-class TextFieldComboBox;
 } // namespace Utils
 
 namespace ProjectExplorer {