Cleanup in gsttypes.c: removed the crazy GList of GHashTables, since the autoplugger will use the GstCaps and element...

Original commit message from CVS:
Cleanup in gsttypes.c:
removed the crazy GList of GHashTables, since the autoplugger will
use the GstCaps and elementfactories instead of the type system.
We don't maintain a list anymore of the elements for the specific
removed unused code in XML loading/saving.

Cleanup in gstelementfactory:
removed the register/unregister methods, register is now implicit when
gst_elementfactory_new is called. _unregister is now _destroy.
Removed logic to register/unregister the types in gsttypes.
added methods to query if the factory can src/sink a GstCaps
Make sure the elementfactory is set in the element_class when a new
element is registered with gst_elementfactory_new.

gst.c: properly register the basic bins
gst_pipeline: use new gstautoplug (next checkin)
gstprops: fixed an error in compatibility check
registry test program changes
plugins: misc changes for the new caps system.