Write out a little brurb before reply text

This makes my reply text look a whole lot more like other people's
reply texts.
Add an "inbox" command

This is just really a super short way to get back to the inbox, which
is pretty much always where I want to be!
Work around a probable bug

I'm not entirely sure what's going on, but it appears that I can end
up in a state where a message exists only in the IMAP__messages table
(and not the MH__messages table).  This ends up causing trouble
because the IMAP synchronizer will attempt to remove it but is unable
to.

While this appears to indicate a bug, in this case it's not actually a
problem so I'm just going to ignore it.