Move Reliability content to the Advanced Administration Handbook

[javiercasares]

There is a lot of content previously added to the Hosting handbook because there was no place to include it.

Now, with the Advanced Administration Handbook, we have some duplicated content, and we need to move / mix some content into the new Handbook.

Reliability

The Reliability page can be included into the Performance and the Cache pages.

Tickets:

• [ ] Update page: Backups #148
• [x] New page: Monitoring #157
• [x] New page: Version Control #158