move connection block schema out of terraform core
move connection block schema out of terraform core

This way it can be used to handle connection values in the communicators
directly without importing terraform.

pdecat/terraform,rnaveiras/terraform,ewbankkit/terraform,apparentlymart/terraform,hashicorp/terraform,rnaveiras/terraform,apparentlymart/terraform,ewbankkit/terraform,apparentlymart/terraform,apparentlymart/terraform,tommynsong/terraform,pdecat/terraform,tommynsong/terraform,ewbankkit/terraform,hashicorp/terraform,pdecat/terraform,tommynsong/terraform,rnaveiras/terraform,hashicorp/terraform,pdecat/terraform,ewbankkit/terraform,apparentlymart/terraform