Update error types to full URLs per DID Resolution spec

[wip-abramson]

While developing the test suite, I noticed that the universal resolver returns error objects with types like : METHOD_NOT_SUPPORTED

Instead, it should be a full URL https://www.w3.org/ns/did#METHOD_NOT_SUPPORTED

See https://w3c.github.io/did-resolution/#errors

[wip-abramson]

See: https://w3c-ccg.github.io/did-resolution-mocha-test-suite/