Replace Irc_message.parse_result with a generic Irc_result.t

Signed-off-by: John Else <john.else@citrix.com>
Add Irc_result to docs

Signed-off-by: John Else <john.else@citrix.com>
Return a Result.t from connect_by_name

Signed-off-by: John Else <john.else@citrix.com>