Request handling refactor complete

Finished* refactoring authorization/token request handling. Requests are now separated into three classes: AuthorizationRequest (sent to the Authorization Endpoint), TokenRequest (sent to the Token Endpoint), and StoredOAuth2Request (stored as part of an OAuth2Authentication for storage when granting & minting tokens). 

*I have updated Sparkl2 and Tonr2 and verified that they both work, fixed unit tests, and done wire tests on our OpenID Connect Server code. We are still in the process of wire-testing some of our more esoteric functionality, but we don't anticipate any issues with that.