[api] fix some problems noted in production

- the buildevent can even more payload
- the request events need a "The one who did it."
- avoid crash in request show with issues
[webui] make parameters optional for save_comments

I wonder why this was never hit by the test suite ;(
[webui] restore display of last declined request in rdiff
[backend] drop the inode number from the deltaid hash, it breaks if the tree is copied

The inode is good for internal stuff, but bad for deltas, as deltas
get published and a redone delta is newly signed and thus end up
different than the old delta.
Copy over the old delta if we have one to ease migration.
[webui] Implement reverse owner "search" on the users home page
[webui] Catch the case where no OBSRootOwner is set
[api] avoid leaking connections in threads

I assume this is a bug in clockwork, but it's easy to work around
[webui] Added more testcases for adding reviewer in requests
[api] catch errors while fetching lastnotifications

There is no harm done - we just refetch later again
[dist] add (api) coverage to the README
[api] add a test for the status_history model

It was meant as finger training in coverage, but it actually found a nasty
bug I introduced in my refactoring
[api] move the matcher out of activexml

It has no coverage outside of test cases
[webui] test cases for comment post methods
[api] ignore indices files for coverage

They are config files really
[backend][api] drop BUILD_UNCHANGED event

 90% of our events are "build unchanged" and we have zero subscribers
add $BSConfig::workerpartitionservers

Currently evaluated in scheduler, should be read and transmitted
by the src server in the future.
[backend] delete no longer needed line
[backend][api] drop BUILD_UNCHANGED event

 90% of our events are "build unchanged" and we have zero subscribers
[api] fake issue servers using webmock

Fetching fate issues seems to be a stub ;(
[dist] update gem versions