Add KYC Service and enable getting user's persona accountId

[ocasta181]

STR-679

Changes:

• Add an endpoint to /users/ that returns the user's persona accountId. It either returns a previously existing persona accountId or creates a new one and returns that.
• Add KYC service for identifying if the user meets the KYC level needed for a transaction

To test:

• Use Create Identity Table migrations#18
• Create a user and hit the /users/persona-account-id endpoint. Confirm a new persona account has been created in the Persona dashboard.
• Run the unit test TestMeetsRequirements() in kyc_tests.go

[auroter]