Add ability to update omnibus provided PostgreSQL to 9.6.1

* Installs postgresql to version specific directory, and symlinks binaries
into /opt/gitlab/embedded/bin
* Adds pg-upgrade option to gitlab-ctl to upgrade the database application and data
* Provides revert-pg-upgrade option to revert the database in case of issue

See merge request !1058

Fix docker patch.

Fix failing master build of the image.

See merge request !1113

fix typo in backups.md

fix minor type in backups.md

if should be (data) not (date) in the followinh section:

> If you separate your configuration backup from your application data backup, you reduce the chance that your encrypted application __date__ will be lost/leaked/stolen together with the keys needed to decrypt it.

See merge request !1110

Add more information on customising NGINX error pages

Include custom_error_pages config in example gitlab.rb
Add image of example error page
Update settings title

See merge request !1112

Include custom_error_pages config in example gitlab.rb
Add image of example error page
Update settings title

* Setup the deploy page and shutdown unecessary services while the
process is running
* Spell out the prerequisites in the documentation for interested users.

[ci skip]

Signed-off-by: Rémy Coutable <remy@rymai.me>

SMTP configuration doc updates

This updates the SMTP configuration docs to include configuration instructions for Rackspace as an email provider. It also includes a blurb on how to manually test the SMTP configuration using the Rails console to send an email (borrowed from the note by @tacid at https://gitlab.com/gitlab-org/gitlab-ce/issues/15460#note_18220405).

See merge request !1111

add SMTP configuration instructions for Rackspace, add info on how to send a test email using Rails console

Extract mailroom idle timeout to an attribute

I'm adding this so we can play with the mailroom idle_timeout that locks when we try to make it hung up.

I'm not certain if this is the way to do it, so I'm open for corrections and or to redo the work completely.

I couldn't find any spec to add on this, so I took the quick path.

cc/ @marin

See merge request !1087

Mattermost 3.5 config update

Followup to https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1104 to add the new config options


Includes the commits from the parent merge request, so it should go in first.

See merge request !1106

fix Redis password issue on Redis-only server

Fix https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1708.

Eliminate unnecessary error messages when running Redis-only server.

Add details about how this only works in 8.14 and up.

See merge request !1107

This adds the new settings outlined in mattermost's release notes here:
https://docs.mattermost.com/administration/changelog.html#release-v3-5-0

* Go into more detail about pg-upgrade

* Use 9.6.1 for new version of PostgreSQL
* Use more explicit logging. Indicate what was done, and be clearer
about what we expect and what goes wrong.

add running Redis server using Omnibus details, Redis HA details, and gitlab.rb.template cleanup

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6471 is proposing removing these details from https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/administration/high_availability/redis.md so lets add them here.

Also cleanup `gitlab.rb.template`.

/cc @marin 

Todo later:
* [ ] Add link to `redis.md` in Omnibus repo from HA section of CE repo (see https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6471#note_18490785)

See merge request !1101

* Update the database upgrade actions to be more clear about what they
are doing
* Move the mocking of helper files out of the individual spec files,
into the main configuration

packagecloud_upload.sh Verify argument count

Update `packagecloud_upload.sh` to account for checking the argument count.

*  also fixed white space on L30 for integer math vs string handling. `expr` is used here for older systems that might have an older `bash`.

Closes #1705

See merge request !1096

fix minor typo in disabling automatic database migration

Minor typo fix.

/cc original author @WarheadsSE

See merge request !1100

fix code formatting in redis.md

Fix code formatting.

See merge request !1098

add details on gitlab_rails['auto_migrate']

Add more details about `gitlab_rails['auto_migrate']`. Still room for improvement.

Related to https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1685

See merge request !1099

* Run analyze_new_cluster.sh after database upgrade
* Make program output clearer

Update `packagecloud_upload.sh` to account for checking the argument count.

*  also fixed white space on L30 for integer math vs string handling. `expr` is used here for older systems that might have an older `bash`.

Cover the case when platform is reported as opensuseleap for pushing packages to package repository.

See merge request !1095

Redis: Autofill master_password based on redis password

Small improvement to Redis / Sentinel setup. If the user forget to inform the `redis['master_password']`, we can try to infer the value from `redis['password']`.

See merge request !1093