[ee] Incorporate DiffService.CommitPatch Gitaly RPC

See merge request !2729

Add language mapping to crowdin.yml

See merge request !2740

# Conflicts:
#   Gemfile
#   Gemfile.lock

And add the project_identifier & api key to be able to work with Crowdin-CLI

Implement new EE-only system note icons

Closes #3205

See merge request !2713

Log Geo file download attempts and status

See merge request !2722

Remove unneeded sidebar class

Closes #3218

See merge request !2738

Add note about restarting repmgrd to ensure it doesn't think it's a
master

Break out configuration, and commands needed into their own sections.

* Clean up section on pgbouncer user information

* Update formatting
* Explain more about prerequisites

* Change layout to clarify differenet stages of the install
* Add instructions for pgbouncer and gitlab-rails
* Remove requirement for database user password.
* repmgrd is automatically setup now, so remove manual steps

EEP only

This reflects the current state of the repmgr in omnibus-gitlab MR 1664

Add the ability to add values to Metric events

See merge request !2730

Fix typo for slot name.

See merge request !2737