Support Matrix CS API 0.4.0

[KitsuneRal]

The new release of Matrix CS API has schemas that are compositions of another type and an additional field in the body schema. The following problems should be solved:

• A combination of $ref and a non-$ref entity under allOf. In the particular cases of CS API it can be remedied by pulling properties of the inner object to the level of the main structure (and that's actually a more transparent description). However, not all (theoretical) cases can be resolved that way, so GTAD has to learn that allOf is allowed to have non-$ref entries.
• Even if the properties are pulled as described above, GTAD fails to flatten the request body schema, instead creating a type definition that depends on itself (corresponding to struct Type : Type in C++). It should further pull out properties out of the schema and turn them into individual parameters of the request.