Support for modular registration of modules

[nmocruz]

I was trying to use this library on a migration to dotnet core.

On the migration, I need to add bundles defined by module

ConfigureModuleServices(IServiceCollection services ...)
        service.AddBundle(pipeline => ....

The problem is that I can not call AddWebOptimizer with a second set of bundles. It doesn't append new bundles. Seems like AddWebOptimizer is intended to be called just once, and there no clear way to reconfigure the list of bundles