use grpc port -1 by default in PyBullet. add grpcClient.py and grpcServer.py

examples/pybullet/examples/grpcClient.py

@@ -0,0 +1,19 @@
+
+import pybullet as p
+
+usePort = True
+
+if (usePort):
+	id = p.connect(p.GRPC,"localhost:12345")
+else:
+	id = p.connect(p.GRPC,"localhost") 
+print("id=",id)
+
+if (id<0):
+	print("Cannot connect to GRPC server")
+	exit(0)
+	
+print ("Connected to GRPC")
+r2d2 = p.loadURDF("r2d2.urdf")
+print("numJoints = ", p.getNumJoints(r2d2))
+