Adding grpc++_unsecure project file, and adding better support for test projects.

build.json

templates/vsprojects/generate_debug_projects.sh

templates/vsprojects/gpr/gpr.vcxproj.filters.template

templates/vsprojects/gpr/gpr.vcxproj.template

...s/vsprojects/gpr_test_util/gpr_test_util.vcxproj.template

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

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

...sprojects/grpc++_unsecure/grpc++.vcxproj.filters.template

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

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

templates/vsprojects/grpc/grpc.vcxproj.template

...projects/grpc_csharp_ext/grpc_csharp_ext.vcxproj.template

...vsprojects/grpc_test_util/grpc_test_util.vcxproj.template

...ects/grpc_unsecure/grpc_unsecure.vcxproj.filters.template

...s/vsprojects/grpc_unsecure/grpc_unsecure.vcxproj.template

templates/vsprojects/vcxproj.filters_defs.include

templates/vsprojects/vcxproj_defs.include

tools/buildgen/plugins/generate_vsprojects.py

vsprojects/dummy.c

vsprojects/global.props