Restructure user docs

[rocketstack-matt]

Feature Request

Description of Problem:

CALM is a solution to a complex problem and has a lot of facets to cope with that complexity. We require high quality documentation to help make it easy for newcomers to CALM as well as to enable folks coming up the learning curve.

Potential Solutions:

Structure the documentation according to diataxis to help users of different levels of expertise or facing specific problems to more readily find the information they required.

The proposed areas would be

• Concepts: walkthrough the core concepts of the schema.
• Guides: explaining how to achieve specific goals.
• Tutorials: learn more in depth aspects of how to work with CALM.
• Reference: technical details on specific aspects of CALM and associated tools.