[CF-metadata] projections

[Jonathan Gregory]

Dear John

> i agree we dont necessrily want to endorse all the complexities of outside 
> standards. OTOH, we should reuse the useful parts, theres no reason to make up 
> new names and parameters. a middle ground would be to officially endorse only 
> what gets explicitly included in the CF Appendix, but to explicitly identify the 
> "authority" from where it comes.

I agree with this middle ground, although we might want to apply changes to
what we were reusing if somehow it didn't fit the CF "style".

Thanks for working on it.

Jonathan