This change makes it possible to replace all of the various
IAntiforgery*** extensibility points via DI.
changes:
- Move functionality out of AntiforgeryWorker into Antiforgery
- Move services to DI (instead of constructed by Antiforgery)
- Cleanup how application/cookie-name is computed
- Merge IAntiforgeryTokenGenerator & IAntiforgeryTokenValidator
- Unseal classes
- Fix use of options in services
- Misc test cleanup
Ryan Nowak