Store qml versions in the metatype system. Instead of just assuming
e.g. "4, 6" or "4, 7" as default, support passing "-1, -1" as versioning
wildcard.

When inspecting the qml meta type system, versions are now stored also
for types that have no qml name / version. The version of the referenting
type is then taken, e.g. there are now entries for "Qt/Object", 4, 7 and
"Qt/Object", 1, 0 (from QmlProject, 1, 0).

Furthermore, some unused methods were removed, and the logic changed insofar
as that a type can have only one direct super type.

Reviewed-by: Thomas Hartmann
Reviewed-by: Marco Bubke