CRS objects are seriously not recommended.

I've removed them from the spec and only refer to them via refs to the original geosjon.org format spec.

Under interoperability considerations (expanded), I push all responsibility for use of non-default CRS onto servers and reiterate that servers must not under any circumstances give out lat,lng data. Doing so creates a world of hurt for developers (I hope we all agree).

cc @geojson/owners @rajrsingh @dr-shorthair @jyutzler and also @elemoine (does this suit your needs, Éric?)