promdash is more useful for most users

Use new makefile to build target, doesn't depend on go being setup.

Don't expect users to know what screen is.

Make it clear what the full config is.

Expand faq.

Document deriv, update/correct docs for rate and delta.

License cleanup

Make documentation for absent() not, uhm, absent

Add an FAQ

Move the rules over to the querying section, that seems more natural.

Add some guidance on recording rules naming.

Also cover how to correctly handle means when aggregating.