There's not much sense in overduplication of documentation
(tends to get stale faster then), still it's not good to
just refer to the code as the PDF/HTML book is less useful
then; maybe drifting towards "recommended" bits with more
"advanced" things being impleentation-defined is better.

This further refines the modular build by making
metadata being a clearly separated feature rather
than having to rely on runtime tests, and also by
moving the code which cares for kernel bits of base
installation (.base list) in a feature of its own.

There's more to it but let's get the ball rolling first.