add experimental vrSyncPlugin, that syncs the position/orientation of a vr controller to a gripper (through a constraint)

This is in C++ and the sync runs at the simulation speed (240 Hz), so there is less lag than in Python.
Modify the pybullet/examples/vr_kuka_setup.py at the end to do this:

plugin = p.loadPlugin("e:/develop/bullet3/bin/pybullet_vrSyncPlugin_vs2010_x64_release.dll")
controllerId = 3
p.executePluginCommand(plugin ,"bla", [controllerId,pr2_cid],[50])

examples/SharedMemory/plugins/vrSyncPlugin/vrSyncPlugin.h

@@ -0,0 +1,25 @@
+#ifndef TEST_PLUGIN_H
+#define TEST_PLUGIN_H
+
+#include "../b3PluginAPI.h"
+
+#ifdef __cplusplus
+extern "C" 
+{
+#endif
+
+//initPlugin, exitPlugin and executePluginCommand are required, otherwise plugin won't load
+B3_SHARED_API int initPlugin(struct b3PluginContext* context);
+B3_SHARED_API void exitPlugin(struct b3PluginContext* context);
+B3_SHARED_API int executePluginCommand(struct b3PluginContext* context, const struct b3PluginArguments* arguments);
+
+//preTickPluginCallback and postTickPluginCallback are optional.
+B3_SHARED_API int preTickPluginCallback(struct b3PluginContext* context);
+
+
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif//#define TEST_PLUGIN_H