og_mailinglist 6.x-1.0-beta3

Split out filter code into its own include file. Variety of small bug and documentation fixes. Ensure that non-utf8 text + subject lines are converted to utf-8. Handle emails better w/o subjects. Added module to provide integration with og_forum.

Issues closed:
#927174: Group address gotten via heuristics instead of parameters from the SMTP agent
#810466: Detect when someone forks a conversation and create a new node
#934344: Patch for an email comes in from mail clients using non utf8 (Japanese)
#928124: We look for PHPMailer; other library users expect phpmailer.
#924468: emails with no subject create nodes with no titles