Use metaclass system to automate generating propertyindex methods for value classes

[oktal3700]

For each new value class we must manually write the methods propertyByIndex, setPropertyByIndex, etc. For a long time I wished to automate this task using the metaclass system (previously known as tuple system). As a first step, we would need to add support for getters and setters in the metaclass system, as there are many property indexes that do not correspond directly to individual data members.

Also consider using a pair of ints for each index in CPropertyIndex (one int for the enum, another int for the metaTypeId of the enum type) as this would remove the requirement to avoid collisions of enum values defined by the index enums of different value classes. (Need to think how this would interact with dbus.)