Completely remove the server window

The outline view in the server window was not designed initially to be
used for what it does now. It's a large and complex to work with, and
should be replaced with something more well though out. Remove all of it
for now since it just makes it more complicated to  modify the source
code.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Remove unnecessary parser thread

It's not necessary to run a thread for each IMAP parser as long as the
access to the stream buffer is synchronized so that two threads does not
modify it at the same time. Remove the thread and complicated logic that
was needed to maintain it, replacing it with a asynchronous dispatch
block.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>