clairify scope parameter definition in backchannel authenticaion request

[Brian Campbell]

On the 8/23 call as a part of discussion on Issue #106 there was general consensus that the description of the scope request parameter should be refined to more clearly reflect the fact that it's the requested scope similar to the scope parameter in other OAuth and OIDC requests. And thus more clearly allow for profile, email, address and phone scopes values as well as other scope values as defined/used by the AS/OP.

[Brian Campbell]

pull request #34 has proposed changes to the scope parameter aimed at addressing this

[Brian Campbell]

merged pull request #34 to refine CIBA scope request parameter test to more clearly reflect the fact that it is the requested scope similar to the scope parameter in other OAuth and OIDC requests and thus more obviously allow for profile, email, address and phone scopes values as well as other scope values as defined/used by the AS/OP (issue #108)