Add documentation

[drpaneas]

Add documentation

Create documentation for SRE and Developers who want either to
contribute or use the Operator. It adds a "docs" directory
and dumps all the related documents:

 * docs/README          - central TOC overview of the documentation
 * docs/gcpconfig       - instructions for GCP Configuration
 * docs/userstory       - how to use it
 * docs/debug           - tips and tricks
 * docs/api             - api description
 * docs/design          - describes the CRDs
 * docs/building        - instruction for building the project
 * docs/development     - devenv setup
 * docs/troubleshooting - common error during dev cycles
 * docs/analysis        - high-level overview of the code

Part of OSD-3248

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: drpaneas
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[mmazur]

I fixed what jumped out at me.

[drpaneas]

I fixed what jumped out at me.

Thank you for your time Mariusz going through the large document. I've approved your suggestions.