Removing java examples from grpc-common

java/pom.xml

java/run_greeter_client.sh

java/run_greeter_server.sh

java/src/main/java/ex/grpc/GreeterClient.java

java/src/main/java/ex/grpc/GreeterGrpc.java

java/src/main/java/ex/grpc/GreeterImpl.java

java/src/main/java/ex/grpc/GreeterServer.java

java/src/main/java/ex/grpc/Helloworld.java