VC/VP verification of context vocabulary

[troyronda]

We need the ability to verify that only context vocabulary is present in a VC, VP, LD Signature. i.e., how do we validate that a JSON-LD document only contains defined vocabulary?

Example Scenarios:

• “newProp”: “bar” added to VC or VP (where newProp is not in the contexts).
• “newProp”: “bar” added to Proof (where newProp is not in the contexts).
• An existing property is set to a value not in context (see https://github.com/hyperledger/aries-framework-go/pull/1698).

note: we should retain the option to ignore missing context vocabulary problems (in general JSON-LD document processing).

[troyronda]

@kdimak i assume there is another PR coming for VPs? (strict mode plus tests)