Ben Cumming authored 7 years ago and Sam Yates committed 7 years ago

Add some C++ API documentation.

* Create C++ API section in docs.
* Document `arb::recipe`: both a class reference along with more explanatory text and best practices guide.
* Add some class documentation of basic types required to understand recipe definition.
* Some in-code comment clean up.
* Change `arb::cell_kind` from a vanilla enum to a scoped enum.