- Made folder/Maildir.py/deletemessage() more tolerant if a message
asked to be deleted already has been.
- In Base.py/copymessageto(), no longer bother calling getmessage()
unless a folder's storemessages() returns true. This will also help
with syncing to LocalStatus if the user deleted messages in the
Maildir since the cachemessagelist() was called.
Fixed save() such that it will be atomic. If the program crashes while
writing, it is guaranteed to have either a complete copy of the old or
the new data.
