[chora] Problem with cached mimetypes in mime.php

[Anil Madhavapeddy]

>
> I noticed a problem when I tried to add a mime type to
> the cache list.

Thanks Todd!  I changed the config file key to 'types' instead.

I'm actually in the middle of a complete rewrite of the MIME functionality
in Chora, so it'll all be replaced real soon hopefully.

Anil