Orm silex simple user

Hey @jasongrimes , I have been trying to implement your stuff in an ORM / Annotation way, making the whole thing quite easier to implement.

Most tests pass except CustomClass and event related one.

I don't really know what to do with that tbh. Most changes are on User and UserManager (now UserRepository) but that's such a huge change from your original files, I don't know if you want to integrate those changes... Maybe I should do my own package, but I wanted to offer you this code before and see if we could find some way to integrate it to yours... Your bundle has helped me a lot, but having an Entity based one is so much easy for me and that needed a lot of changes...

Tell me :)