More robust witness querying

[pfeairheller]

Witness querying for key state for and purpose needs to be improved to support querying across all appropriate witnesses with results being compared for correctness. Once this algorithm is in place, it needs to be applied in all cases where AIDs are resolved that have witnesses.

This includes (but is probably not limited to):

• OOBI resolution
• Credential issuance
• Credential verification
• Delegation approval
• Peer-to-peer message exchange