Strip trailing NULL bytes from INFO response.

Same as 0158148 for the releases branch.
Changelog for #778
Merge pull request #778 from bmorg/fix_seedlink_trailing_null_bytes

SeedLink: Strip trailing NULL bytes from INFO responses
Adding ORFEUS FDSNWS implementation.
reading SAC: prepending "19" in case of 2 digit year header field +
warning (see #779)
Don't create empty objects
Small fix making lots of StationXML file writeable
The attach response option will now request once per channel.

This will be much faster on average compared to the previous
solution. The previous solution requested once per station
for all time frames resulting in potentially hundreds of
downloaded responses for one trace making in unbearably
slow in some cases. This should likely be backported to the
releases branch.
Updating changelog
Merge branch 'releases'