Tests and fixes. - Factor MailGW message parsing into a separate class, thanks to John Kristensen who did the major work in issue2550576 -- I wouldn't have attempted it without this. Fixes issue2550576. (Ralf) - Now if the -C option to roundup-mailgw specifies "issue" this refers to an issue-like class. The real class is determined from the configured default class, or the -c option to the mailgw, or the class resulting from mail subject parsing. We also accept multiple -S options for the same class now. (Ralf) - Add regression test for message-id generation if message id is missing in a message - Add regression tests for Option parsing (-S and -C options)