Improve installation docs

[initvector]

The developer docs has an "Installation" page that is pretty bare bones. However, there are more comprehensive, server-specific installation docs under the "Backends" section. These should probably be at least referenced from the installation page.

[charrondev]

I'm thinking we should also have a localhost development setup guide for for MacOS as well. This should be more user specific than the server installation requirements.

The doc structure would then be:

Installation (general overview, links to the other 2)

• Development Quickstart
• Production Requirements