Update documentation

[willingc]

Based on feedback from @ellisonbg's experience with CP deployment, we should update the README and Sphinx docs.

• Simplify README moving most installation instructions to Sphinx docs
• Add some UI screenshots to README
• Add a checklist for pre-deployment tasks
  - Obtain domain name
  - ssh key creation
  - DNS routing for server and domain name
  - encourage letsencrypt (which is working well with current Ansible scripts)
• Add user friendly walkthrough of consolidated configuration file and suggested settings

[rushgeo]

Working on checking the README vs. Sphinx, and testing the deployment and seeing if I have any documentation improvement ideas.

[willingc]

Great @rushgeo

[cmyceloso]

link to the Cal Poly deployment in the README is no longer working, it's now located here.