add physics server loopback (both client and server in the same process, using shared memory)

add physics server direct (client and server in the same process, directly processing commands without shared memory transport mechanism)

examples/SharedMemory/PhysicsDirectC_API.cpp

@@ -0,0 +1,14 @@
+#include "PhysicsDirectC_API.h"
+
+#include "PhysicsDirect.h"
+
+
+
+//think more about naming. The b3ConnectPhysicsLoopback
+b3PhysicsClientHandle b3ConnectPhysicsDirect()
+{
+	PhysicsDirect* direct = new PhysicsDirect();
+	bool connected = direct->connect();
+	return (b3PhysicsClientHandle  )direct;
+}
+