Logging twitters should be better about conversations

[jgross@mit.edu]

In perl-logging (hopefully soon to be merged), twitters are logged based on who they're from (or to? or both?). Conversations, especially multi-participant conversations, should have a better story for logging. (Fixing this, once perl-logging has been merged, will simply consist of coming up with the better story, and overriding the method in Message.pm that generates log file names.)