verificationMethod and authentication must be arrays

[domwoe]

I've changed the DIDDoc building/verification steps a bit. The ids of the base did doc must not be present in any of the diddocContent elements not only in verificationMethod and authentication.

An example would be:

"diddocContent": {
"assertionMethod": [
    "did:example:123456789abcdefghi#keys-1",
    {
      "id": "did:example:123456789abcdefghi#verkey",
      "type": "Ed25519VerificationKey2020", 
      "controller": "did:example:123456789abcdefghi",
      "publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV"
    }
  ],
}

where the same id would be redefined in an assertionMethod block.

Resolves #47

Signed-off-by: Dominic Wörner dom.woe@gmail.com