[O01.01.12.07] Rewrite getting-started and per-library docs

[dotnetcadet]

Summary

Documentation: rewrite getting-started and author per-library OVERVIEW/DESIGN docs.

Acceptance Criteria

• The getting-started guide is rewritten.
• Each library has OVERVIEW and DESIGN docs.
• Docs reflect the ratified design decisions D1-D5.

Standards and Compliance

• Documentation concern.