single function for important streams, with memcached support

single function for important streams, with memcached support

I moved the 4 streams for a user (with friends, faves, replies,
personal) into functions on the User object. Added a helper function
in Notice for making notice streams. Also, will fetch notice streams
out of the memcached server, if possible. Made the API, RSS, and HTML
output all use the same streams (hopefully cached).

Added some code to Notice to blow the cache when a notice is posted.
Also, added code to favor and disfavor actions to blow the faves
cache, too.

darcs-hash:20080928120119-5ed1f-ead542348bcd3cf315be6f42934353154402eb16.gz