RFC: show/hide deleted messages

[Peter Bloomfield <PeterBloomfield bellsouth net>]

I propose the following changes in the way Balsa handles the 
showing and hiding of deleted messages.

1. The default for a new user should be 'Hide deleted messages'.
2. If deleted messages are shown:
    a. When the current message is deleted, Balsa displays the
       next message automatically; if the deleted message is the
       head of a collapsed (sub)thread, the displayed message is
       the first child, and the thread is expanded far enough to
       reveal the child;
    b. When the current message is undeleted, it continues to be
       displayed;
    c. The `Next Message' and `Previous Message' menu items and
       toolbar buttons skip over deleted messages.

Comments?