they will remain for internal use only, so should not be mentioned in this
public spec

this reverts the documentation part of 67fade5f

to prevent sphinx from complaining about these not being included.

double back-quote (``) are not interpreted when inside a emphasis block.

Promote "Resolution" to a new top-level section, because it's now rather
voluminous.

As part of this document the resolver limitations of identifiers.org, that get
in the way of PID contextual information.

Closes T1015
Closes T1223

Closes T1041

Closes: T335