More work on the C/C++ plugin system for pybullet/C-API:

Add preTickPluginCallback/postTickPluginCallback
User pointer for b3PluginContext, to store objects (class/struct instances)
Pass ints and floats as optional argument for plugin executePluginCommand

examples/SharedMemory/PhysicsServerCommandProcessor.h

@@ -91,6 +91,7 @@ public:
 	virtual void replayLogCommand(char* bufferServerToClient, int bufferSizeInBytes );
 
 	//logging of object states (position etc)
+	void tickPlugins(btScalar timeStep, bool isPreTick);
 	void logObjectStates(btScalar timeStep);
 	void processCollisionForces(btScalar timeStep);