Add CleanGenerated and Regenerate targets to GeneratedLibraries.proj
Add CleanGenerated and Regenerate targets to GeneratedLibraries.proj

Useful for debugging code generation.

jskeet/google-api-dotnet-client,googleapis/google-api-dotnet-client,googleapis/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,ivannaranjo/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,ivannaranjo/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,ivannaranjo/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,jskeet/google-api-dotnet-client,ivannaranjo/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,googleapis/google-api-dotnet-client,jskeet/google-api-dotnet-client