[api] add routes to get XML view of comments

issue 545
[api] test case for set_bugowner for groups
[api] implement delete_comment
[api] implement post to request comments
[api] remove package and project from event subscription

It was never used and we came to the conclusion we can't and don't
want to support per package subscriptions, but make use of filters
for the same - it's more powerful
[api] test that previous commenters get mails
[backend] improve rename content.new error message
[api] test case for set_bugowner for groups
[webui] Fix forum link
[backend] do not allow illegal vendor strings for media 12
[backend] allow to limit product views to a given product
[backend] option for removing directory trees in kiwi products
[api] support product listing per project
[api] provide product listing in own xml structure, sort by cpe and export it as well
[api] include people mentioned with @<login> as commenters

This is kind of faking, but I don't want to have yet another receiver role
[dist] fix obs-server.spec file list
[webui] fix another place where tizen is to be used instead of meego
[api] fallback to query all bugzilla states, if the api call to list just the new ones fails since two days.

That way we get finally updates again. It helps hopefully also bugzilla to avoid timeouts by requesting
smaller lists after some timeout again.
[api] refactor issue tracker a bit
[api] fix revoke/decline open requests on package removal