Add Redis identity test

Run identity tests against a redis DbContext.

@lajones Can you review the redis stuff.  I copied this from Redis.Functional pretty much as is?  I had to disable 2 tests due to key generation not working.
Nope. The service should be added whenever you call UseRedis(). If you like there are some examples of that service being used RedisSequenceValuegeneratorTest.cs in the Redis Tests (not the Functional Tests, the other project).