Add type to quark and type to string conversions.

Add type to quark and type to string conversions.

Original commit message from CVS:
* docs/design/part-TODO.txt:
* gst/gstformat.c: (_gst_format_initialize), (gst_format_get_name),
(gst_format_to_quark), (gst_format_register):
* gst/gstformat.h:
* gst/gstquery.c: (_gst_query_initialize),
(gst_query_type_get_name), (gst_query_type_to_quark),
(gst_query_type_register):
* gst/gstquery.h:
Add type to quark and type to string conversions.