Server parameters are a complex registry system intimately often invoked via IDL generated classes. They can be set at both runtime via command and at startup via config files or arguments. The various relevant pieces live in src/mongo/db/commands/ and src/mongo/idl. This section should discuss how we register server parameters, how they are set (including setParameter/getParameter commands), and how they are accessed during runtime.

We should document it as a new file docs/parameters.md.

This is intended to be abstract documentation, describe relationships and state transitions not code in common language.