allow pybullet to connect to GRPC server. (need to use flag --enable_grpc in premake build system)

add grpcPlugin, it can work in GUI, SHARED_MEMORY_SERVER, DIRECT and other modes.
example script to start server from pybullet:
import pybullet as p
p.connect(p.GUI)
#if statically linked plugin
id = p.loadPlugin("grpcPlugin")
#dynamics loading the plugin
#id = p.loadPlugin("E:/develop/bullet3/bin/pybullet_grpcPlugin_vs2010_x64_debug.dll", postFix="_grpcPlugin")

#start the GRPC server at hostname, port
if (id>=0):
	p.executePluginCommand(id, "localhost:1234")

Only in DIRECT mode, since there is no 'ping' you need to call to handle RCPs:
numRPC = 10
while (1):
	p.executePluginCommand(id, intArgs=[numRPC])

examples/pybullet/premake4.lua

@@ -3,6 +3,17 @@
 project ("pybullet")
 		language "C++"
 		kind "SharedLib"
+
+		if _OPTIONS["enable_grpc"] then
+				initGRPC()
+				
+				 files {
+                  "../../examples/SharedMemory/PhysicsClientGRPC.cpp",
+                  "../../examples/SharedMemory/PhysicsClientGRPC.h",
+                  "../../examples/SharedMemory/PhysicsClientGRPC_C_API.cpp",
+                  "../../examples/SharedMemory/PhysicsClientGRPC_C_API.h",
+                }
+		end
 		
 		includedirs {"../../src", "../../examples",
 		"../../examples/ThirdPartyLibs"}

examples/pybullet/pybullet.c

@@ -437,7 +437,7 @@ static PyObject* pybullet_connectPhysicsServer(PyObject* self, PyObject* args, P
 			case eCONNECT_GRPC:
 			{
 #ifdef BT_ENABLE_GRPC
-				sm = b3ConnectPhysicsGRPC(hostName.c_str(), tcpPort);
+				sm = b3ConnectPhysicsGRPC(hostName, tcpPort);
 #else
 				PyErr_SetString(SpamError, "GRPC is not enabled in this pybullet build");
 #endif