- created a PersonManager that keeps track of the names of all email addresses

- created a PersonManager that keeps track of the names of all email addresses
  ever seen. this will probably need to be intelligently trimmed, but will be
  used for fast loading of messages from slow sources.

- moved initialization and shutdown to Redwood::start and ::finish in sup.rb.

- poll#initialize no longer automatically starts a thread. you must call
  #start_thread. (because sup-import now calls Redwood::start which initializes
  all managers, including pollmanager, and it certainly doesn't make sense to
  have anything threaded during import)

- misc. comment improvements

git-svn-id: svn://rubyforge.org/var/svn/sup/trunk@113 5c8cc53c-5e98-4d25-b20a-d8db53a31250