Merge pull request #2440 from  klamontagne/master

Don't setuid the repositories on installation
Small fixes to the installation guide and check task
Port changes from #2803
Dont allow gitlab be loaded in iframe
Show only ≤16 lines of code in a discussion (fix issue #2860).
Replacing the manual parsing of the /etc/group file with the equivalent call from the Etc class in the Ruby standard library. This has the benefit of supporting additional platforms (e.g. OS X).
Code deduplication using inheritance for GroupDetail
Update step 5 "database" (Issue #2894)

Made it a bit clearer what step 5 is for to stop people skipping it. This time with a relative link.
preparing for gitlab-shell
Make gitlab works with gitlab-shell
update installation docs
remove update_repository calls
Fix satellites to use filesystem. Correct post-receive user finder
Internal API
remove gitolite stub
Fix typo.
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updated
remove unexisting stubs