(NC-138) Move class endpoint under environments

This changes the url structure to represent that an instance of a class exists
within an environment. Before this it wasn't possible to distinguish between
different versions of a class across environments properly.
Extract common "/v1" prefix to a context
Refactor crd-resource to accept a vector path and a map of url attributes
Merge pull request #31 from pcarlisle/nc-138-environment-on-class-url

(NC-138) environment on class url