The problem is cr_mime_types is not an extension to mime_type map. It is a mime type listing that happens to include an
extension I think the right answer is a cr_extension_mime_type_map table for the mapping
(which could be populated at startup I guess) into which
new extension - mime type mappings are inserted.
You do want to map multiple extensions into one mime type
and duplicate mime types in cr_mime_types is a pretty ugly thing from the standpoint of pulling content out (I think
there are a number of places it is assumed mime type is
unique in that table).
