Add checks to db verifier.

[aljones15]

@PatStLouis @BigBlueHat adds options.checks = ['poof'] to the db verifier endpoint.
This is how we usually let implementers specify options that have been deprecated by the VC API, but
they haven't had the time or resources to correct on their endpoints.

[BigBlueHat]

@aljones15 fwiw, these are also being used on the vpVerifier endpoints in the VCDMv2 test suite:
https://github.com/w3c/vc-data-model-2.0-test-suite/blob/00fa18a7b676959e7aa5e4b8774a7ce049f9c0d0/tests/10-vcdm2.js#L214
and
https://github.com/w3c/vc-data-model-2.0-test-suite/blob/00fa18a7b676959e7aa5e4b8774a7ce049f9c0d0/tests/10-vcdm2.js#L809

[aljones15]

@aljones15 fwiw, these are also being used on the vpVerifier endpoints in the VCDMv2 test suite: https://github.com/w3c/vc-data-model-2.0-test-suite/blob/00fa18a7b676959e7aa5e4b8774a7ce049f9c0d0/tests/10-vcdm2.js#L214 and https://github.com/w3c/vc-data-model-2.0-test-suite/blob/00fa18a7b676959e7aa5e4b8774a7ce049f9c0d0/tests/10-vcdm2.js#L809

good call here will make those changes in a moment.