Connect to database with git user, not gitlab
Run db:setup and db:seed_fu before gitlab:setup
Added relative urls to other documentation files, removed duplicate debian update commands
Nginx: edit actual file instead of symlink
Added creation of pids directory to fix #2995, replaced deprecated nginx init.d command with service one, some more clean-up
Merge pull request #2998 from axilleas/master

Minor changes to installation and databases docs.