Show IRC server error messages when unexpected
Handle ERROR replies from IRC servers, displaying the error message
in the status buffer.
Add method 'disconnectExpected' to CoreNetwork to expose when a
disconnect is expected. As we're expecting a server error message
when issuing QUIT, hide it to avoid showing redundant information.
This fixes users getting disconnected by the server without any way
to find out why.
Resolves GH-238.
(cherry picked from commit
56b2bf3a1a742971a5de7ced1b57024424fc78b8)