Improve CLI output when a DID fails verification

[thobson88]

When using the trustchain-cli did verify CLI command in the case of a DID that fails the verification process, the output should give a meaningful "Verification Failed" message.

Currently it prints the Rust error variant to the terminal.

Example:

$ trustchain-cli did verify --did did:ion:test:EiByIMb7iIuvToiU299nmRIS4oA3tjCN7mhARaeIdEQddA
Error: CommitmentFailure(FailedContentVerification("[[{\"kty\":\"EC\",\"crv\":\"secp256k1\",\"x\":\"0cXIVhXNPJG9tumd0ZYDfrPFAnk9r_OLIbPTA9N-04I\",\"y\":\"f9Cfa4kOhaER6yUIlX3edeDI-6w3mPEUMnokcSzuA_8\"}],[\"https://www.safeparking.co.uk\",\"https://payments.safe-parking.co.uk\"]]", "{\"deltas\":[{\"patches\":[{\"action\":\"replace\",\"document\":{\"publicKeys\":[{\"id\":\"Bwe-yO7L8nCUkZaUZehuKPqXnNeeKU4drzc6if6ixKQ\",\"type\":\"JsonWebSignature2020\",\"publicKeyJwk\":{\"kty\":\"EC\",\"crv\":\"secp256k1\",\"x\":\"0cXIVhXNPJG9tumd0ZYDfrPFAnk9r_OLIbPTA9N-04I\",\"y\":\"f9Cfa4kOhaER6yUIlX3edeDI-6w3mPEUMnokcSzuA_8\"},\"purposes\":[\"assertionMethod\",\"authentication\",\"keyAgreement\",\"capabilityInvocation\",\"capabilityDelegation\"]}],\"services\":[{\"id\":\"TrustchainID\",\"type\":\"Identity\",\"serviceEndpoint\":\"https://www.safeparking.co.uk\"},{\"id\":\"payment-url\",\"type\":\"WebUrl\",\"serviceEndpoint\":\"https://payments.saefparking.co.uk\"}]}}],\"updateCommitment\":\"EiCTWZfZJQnJccs-o01Difv7wQZeZ7TUhtexIin2A0DkHA\"},{\"patches\":[{\"action\":\"add-services\",\"services\":[{\"id\":\"trustchain-controller-proof\",\"type\":\"TrustchainProofService\",\"serviceEndpoint\":{\"controller\":\"did:ion:test:EiBUjEaDDN1ROq6WgtBgIqpQZAZRu5XKNroOshi_sIDzsw\",\"proofValue\":\"eyJhbGciOiJFUzI1NksifQ.IkVpQXpQU2ZfOUZucjBiUExDbHlKcGVEWmtCQk9FN1M2elZ4Sjh1d0tUV1otc3ci.P5NZ2uwkRDhREcT19MExhJk6E3poRxAlmpcek42V2fdf688pmKK4v4MIDSgXF_JAWdkmGVEYRg4kdopD8OUb6A\"}}]}],\"updateCommitment\":\"EiBNMT54InEMhxdZOIFM5v-bFrcWKi8EX_Rch0k-lZ9lTA\"},{\"patches\":[{\"action\":\"add-services\",\"services\":[{\"id\":\"trustchain-controller-proof\",\"type\":\"TrustchainProofService\",\"serviceEndpoint\":{\"controller\":\"did:ion:test:EiC8hnHRr8kZUFThypBKFsHuzY8jhs4KttnLeJymF-upRQ\",\"proofValue\":\"eyJhbGciOiJFUzI1NksifQ.IkVpQXc1NkR5bXhWSWdneUFINV9uQXQxYWhnbEl2YWxPc254cEl0ZC1wN2hnMlEi.Pa3Qi-Bknh7gnt-2Lcf7hsmQ0ylklJZreOODp0aNZugsrLrL8uI-EsGqQOKckq-hDSP-ZrN6JF02XL2kArjSmA\"}}]}],\"updateCommitment\":\"EiC355nJqmgqJKDbZS-VGj5J7feAffjPLreULIydyN6gqw\"}]}"))