Extension contexts are too broad

[lmckenzi]

Most (all?) of the extensions defined in this IG have a context of 'Element'. However, the intended scope of the extensions is clearly narrower than "any possible element on any possible resource". Please define the extensions to have contexts appropriate to their intended use.

Also, the package indicates this is an HL7 International U.S. Realm IG, but if that's the case, the sponsor needs to be an HL7 work group, not MITRE.