ProxyGenerationOptions in DynamicProxy2

As per discussion here https://github.com/autofac/Autofac/issues/504 I added option to provide ProxyGenerationOptions while building proxy objects. 

I also added the ability to put more than one InterceptAttribute per class since currently there is no way to do this using attributes although you're able to add it through the code.

I created the accompanying unit test to show how you're supposed to use it. I had to slightly modify the current unit tests since I had to change the test classes to add functionality needed to test various ProxyGenerationOptions scenarios.

All the tests are passing, both existing and new ones.

I plan to write a few blog posts describing this addition and I can update the documentation as well.