Possible solution for #534 (Problem with FilterAttributes in the MVC+WebForms project)

Added a chain to ```AutofacDependencyResolver.Current``` where we try to
- cast ```DependencyResolver.Current``` to ```AutofacDependencyResolver```
- get service ```AutofacDependencyResolver``` from the container
- get from the static field if number of instances equals 1

That doesn't solve the root of the issue but could mitigate it.

Made for #534 (Problem with FilterAttributes in the MVC+WebForms project)