[api] 2 small fixes for the test suite
[api] test build failure mail
[api] put the log file in raw mode in the mail

HTML escaping is cool - outside of mails :)
[api] include some headers in the build fail mail header
[api] add threading support for build failure mails

And enable actual sendmail
[api] some changes to the event mails

- don't set reply-to but from
- put all receivers in the same email, so they can share thoughty by group-reply
- use realnames in mail headers