Allow multiple Intercept attributes

Without this, you can use only one InterceptAttribute per class/interface
Enable users to provide ProxyGenerationOptions

Users can now provide their own ProxyGenerationOptions - enabling them to use mixins, IProxyGenerationHook to specify which methods could be intercepted or IInterceptorSelector which enables users to provide valid combination interceptor/methods to intercept
Update AttributedInterfaceInterceptionFixture.cs

Updated tests
Update ClassInterceptorsFixture.cs

Updated tests
Update InterceptTransparentProxyFixture.cs

Updated tests
Update InterceptTransparentProxyFixture.cs

Updated tests
Update ClassInterceptorsFixture.cs

Fixed tabbing
Update AttributedInterfaceInterceptionFixture.cs

Fixed tabbing
Update InterceptorsChosenByMetadataFixture.cs

Updated tests
Update InterceptTransparentProxyFixture.cs

Updated tests
Update RegistrationExtensions.cs

Fixed tabbing
Update RegistrationExtensions.cs

Removing copy-paste blocks
Update AttributedInterfaceInterceptionFixture.cs

Reverted to original tests
Split Option tests from non-option ones
Added comments
Merge pull request #505 from IvanFeric/master

ProxyGenerationOptions in DynamicProxy2