Generating grains in project contaning "Cluster" namespace breaks sourcegen

[jupjohn]

When generating grains in a project whose root namespace contains *.Cluster.* (e.g. Jammehcow.SomeCoolApplication.Cluster.Contracts.csproj), source generation generates uncompilable code. Since generated code contains references to the Cluster type, the type conflicts with the implementing project's namespace.

Proto.Actor version: 1.0.0-rc4.6

[jupjohn]

I've seen this approach in other projects: prefixing your types with global::Your.Fully.Qualified.Namespace.Class will fix the conflict.

namespace Jammehcow.SomeCoolApplication.Cluster.Contracts
{
    public abstract class MyGrainBase
    {
        // This would fail to compile
        private readonly Cluster _cluster;

        // This resolves correctly
        private readonly global::Proto.Cluster.Cluster _cluster;
    }
}

If this looks like a decent way to resolve this I'm happy to fix and test myself, then PR it in.