Checks if @subset is a subset of @superset, i.e. has the same structure name and for all fields that are existing in @superset, @subset has a value that is a subset of the value in @superset.
a potentially greater #GstStructure
Return: %TRUE if @subset is a subset of @superset
See Implementation
Checks if @subset is a subset of @superset, i.e. has the same structure name and for all fields that are existing in @superset, @subset has a value that is a subset of the value in @superset.