Resolve JFV vs HTTPbis Header Structure

[handrews]

We reference https://tools.ietf.org/html/draft-reschke-http-jfv-07 but it turns out there has been a complex history:

reschke-http-jfv-00 through 04
ietf-httpbis-jfv-00 through 02
then it split, with the JSON work going back to reschke-http-jfv-05 through 07, but the HTTPbis work going forward as an abstract data model for headers in ietf-httpbis-header-structure-00 through 01 (with 02 in the works).

JFV: https://tools.ietf.org/html/draft-reschke-http-jfv-07
Header structure: https://tools.ietf.org/html/draft-ietf-httpbis-header-structure-01

We should sort out what is going on here, and also definitively figure out how to address existing headers, particularly those that we recommend using in hyper-schema's targetHints and headerSchema, should be represented.