big refactoring of visual studio projects, started using nuget

templates/vsprojects/vs2010/gpr.vcxproj.template

templates/vsprojects/vs2010/gpr_test_util.vcxproj.template

templates/vsprojects/vs2010/grpc.vcxproj.template

templates/vsprojects/vs2010/grpc_csharp_ext.vcxproj.template

...vsprojects/vs2010/grpc_csharp_ext_shared.vcxproj.template

templates/vsprojects/vs2010/grpc_unsecure.vcxproj.template

templates/vsprojects/vs2010/vcxproj.filters_defs.include

templates/vsprojects/vs2010/vcxproj_defs.include

templates/vsprojects/vs2013/grpc++.vcxproj.filters.template

templates/vsprojects/vs2013/grpc++.vcxproj.template

templates/vsprojects/vs2013/grpc.sln.template

templates/vsprojects/vs2013/grpc.vcxproj.filters.template

templates/vsprojects/vs2013/grpc.vcxproj.template

templates/vsprojects/vs2013/grpc_csharp_ext.vcxproj.template

...vsprojects/vs2013/grpc_csharp_ext_shared.vcxproj.template

templates/vsprojects/vs2013/grpc_test_util.vcxproj.template

.../vsprojects/vs2013/grpc_unsecure.vcxproj.filters.template

templates/vsprojects/vs2013/grpc_unsecure.vcxproj.template

tools/buildgen/generate_projects.sh

vsprojects/.gitignore