Use factory to create entities.

    * src/dynamic_graph/entity.py,
    * src/entity-py.cc: the name of the entity class to be created is now given
      as input to the constructor of Entity python class.

src/dynamic_graph/entity.py

@@ -12,13 +12,12 @@ class Entity (object) :
     
     object = None
 
-    def __init__(self, name):
+    def __init__(self, className, instanceName):
         """
         Constructor: if not called by a child class, create and store a pointer
         to a C++ Entity object.
         """
-        if not self.object :
-            self.object = wrap.create_entity(self, name)
+        self.object = wrap.create_entity(className, instanceName)
 
     @property
     def name(self) :

src/entity-py.cc

@@ -9,6 +9,7 @@
 //#include <string>
 
 #include <dynamic-graph/entity.h>
+#include <dynamic-graph/factory.h>
 
 using dynamicgraph::Entity;
 using dynamicgraph::SignalBase;
@@ -27,14 +28,16 @@ namespace dynamicgraph {
       */
       PyObject* create(PyObject* self, PyObject* args)
       {
-	char *name = NULL;
+	char *className = NULL;
+	char *instanceName = NULL;
 	
-	if (!PyArg_ParseTuple(args, "s", &name))
+	if (!PyArg_ParseTuple(args, "ss", &className, &instanceName))
 	  return NULL;
 	
 	Entity* obj = NULL;
 	try {
-	  obj = new Entity(name);
+	  obj = dynamicgraph::g_factory.newEntity(std::string(className),
+						  std::string(instanceName));
 	} catch (dynamicgraph::ExceptionFactory& exc) {
 	  PyErr_SetString(error, exc.getStringMessage().c_str());
 	  return NULL;