replace all grpc-common occurances with examples

README.md

doc/grpc-auth-support.md

doc/interop-test-descriptions.md

examples/README.md

examples/cpp/README.md

examples/cpp/cpptutorial.md

examples/cpp/helloworld/README.md

examples/csharp/README.md

examples/csharp/route_guide/README.md

examples/node/README.md

examples/node/route_guide/README.md

examples/objective-c/auth_sample/README.md

examples/objective-c/helloworld/README.md

examples/objective-c/route_guide/README.md

examples/php/README.md

examples/php/route_guide/README.md

examples/python/helloworld/README.md

examples/python/route_guide/README.md

examples/ruby/README.md

examples/ruby/grpc-demo.gemspec