Refactor TokenGranter code

[aanganes]

Justin and I had a conversation with Dave Syer today, and decided it would be worth taking a look at how we could move the custom token generation/enhancement code, which we currently have in our TokenGranter impl, into the token service layer instead.

This will change the TokenService interface, which the SECOAUTH team is OK with re-evaluating. We also talked about the TokenService interface having create, enhance, and finish methods.

I will fork our code and push up a new branch to work on these changes.

[aanganes]

Finished, code is in https://github.com/jricher/OpenID-Connect-Java-Spring-Server/tree/refactor_tokengranter_code. I have submitted a pull request to the SECOAUTH team for the changes I made to their code. The pull request is located here: spring-attic/spring-security-oauth#26.

[aanganes]

The SECOAUTH team no longer wishes to refactor in this manner. Instead, Dave has suggested adding a TokenEnhancer interface, similar to TokenStore, and leaving it as an implementation detail for individual TokenService implementations.

[aanganes]

Addressed by remote branch here: https://github.com/mitreid-connect/OpenID-Connect-Java-Spring-Server/tree/issue52