* Use a more complete API to introspect SPA types
* Avoid the need for the Tables enumeration; the tables
are now registered with a string
* Avoid the need for initialization, work directly on spa_types
and other static data
* Allow working with Object pods that are not Params;
the PARAMS table was previously hardcoded in the pod implementation
* Add a different dynamic type registration system, closer to
how spa type works. The only regression is that we can no longer
register additional custom object fields (custom SPA_PROP_* for example),
but this feature can be re-added later
