Some file names on disk don't match class names

See https://github.com/dotnet/orleans/pull/10
For example:
[ActivationID.cs](https://github.com/dotnet/orleans/blob/9283c667f647ec9caf4ec98cf401362c66fa879d/src/Orleans/IDs/ActivationID.cs) 
[GrainID.cs](https://github.com/dotnet/orleans/blob/9283c667f647ec9caf4ec98cf401362c66fa879d/src/Orleans/IDs/GrainID.cs) 
(note upper-case D in file name, but not in class name)
