Better message for failed pushes because of git hooks

Conflicts:
	lib/gitlab/git_access.rb
	spec/lib/gitlab/git_access_spec.rb
add rebuilding of authorized_keys to docs
add correct path to rebuild-keys doc
Merge branch 'rebuild-keys' into 'master'

Rebuild keys

This was clearly lacking for the documenation.

See merge request !1267
Add CRON=1 backup setting for quiet backups
Explain why we create a StringIO
you have to update gitlab shell for gitlab 7.5
Merge branch 'shell220' into 'master'

Add GitLab shell update to update guide

See merge request !1269
Possibility to create Milestones or Labels when Issues are disabled
Merge branch 'milestones_labels' into 'master'

Possibility to create Milestones or Labels when Issues are disabled

https://dev.gitlab.org/gitlab/gitlabhq/issues/1682

See merge request !1270
Add missing timestamps to the 'members' table
Merge branch 'members_table_timestamps' into 'master'

Add missing timestamps to the 'members' table

In 20140914145549_migrate_to_new_members_model.rb we forgot to set the
created_at and updated_at times for new records in the 'members' table. This
became a problem after commit c8e78d972a5a628870eefca0f2ccea0199c55bda which
was added in GitLab 7.5. With this migration we ensure that all rows in
'members' have at least some created_at and updated_at timestamp.

See merge request !1272
start gitlab after mysql tweaks
Merge pull request #8319 from bbodenmiller/patch-12

start gitlab after mysql tweaks
Merge branch 'backup-cron-mode' into 'master'

Backup cron mode

If you have your server configured to receive emails containing the output of
cron jobs it is annoying to get long spammy emails from the backup script. This
change adds a 'cron mode' that makes the backup script silent unless something
goes wrong during the backup.

See merge request !1268
More explicit wording of the documentation.
The release manager handles all releases
Establish ownership of security releases
Bump gitlab-shell
Formatting and sequence of contrubution paragraphs.