Support user verification

[Samjna-nh]

If the relying party set the user verification requirement option to required, the authenticator should return data with the UV flag on, or fail if it cannot do the user verification (spec).
What other virtual authenticators usually do is to add an argument in the constructor to indicate whether the authenticator can do the user verification. And when create / get you compare the setting with the options from RP to update flags / throw errors.
At least, a simple implementation that allow you customize the flags when doing create / get satisfies most cases, otherwise there's no way to do some tests with an RP requiring user verification.

[bodik]

would this be resolved by #15 ?

[Samjna-nh]

Yes, exactly what I want.
Still it would be an option to have a user verification option in the constructor or (create & get) though, but that PR solves most problems.

[bodik]

thank's for review. i'll try to get the PR merged but no guarantees on timeframe thou ;/