Added rank handling at component creation

At creation if no rank specified the component will be place last, else you can pass an integer representing an absolute rank or two specials strings 'last' or 'first'

EditorialModel/model.py

     ## Return a new uid
     # @return a new uid
     def new_uid(self):
-        used_uid = self._components.keys()
+        used_uid = [ int(uid) for uid in self._components['uids'].keys()]
         return sorted(used_uid)[-1] + 1 if len(used_uid) > 0 else 1
 
     ## Create a component from a component type and datas
     #
+    # @note if datas does not contains a rank the new component will be added last
+    # @note datas['rank'] can be an integer or two specials strings 'last' or 'first'
     # @param component_type str : a component type ( component_class, component_fieldgroup, component_field or component_type )
     # @param datas dict : the options needed by the component creation
+    # @throw ValueError if datas['rank'] is not valid (too big or too small, not an integer nor 'last' or 'first' )
     def create_component(self, component_type, datas):
-        datas['uid'] = self.new_uid
-        em_component = self.emclass_from_name(component_type)(datas, self)
+        
+        em_obj = self.emclass_from_name(component_type)
+
+        datas['uid'] = self.new_uid()
+        em_component = em_obj(datas, self)
 
         self._components['uids'][em_component.uid] = em_component
         self._components[self.name_from_emclass(em_component.__class__)].append(em_component)
+
+        em_component.rank = em_component.get_max_rank()
+
+        create_fails = None
+
+        if 'rank' not in datas:
+            if isinstance(datas['rank'], int) or datas['rank'] == 'last':
+                em_component.set_rank(datas['rank'])
+            elif datas['rank'] == 'first':
+                em_component.set_rank(1)
+            else:
+                create_fails = ValueError("Invalid rank : '"+str(datas['rank'])+"'")
+                self.delete(em_component.uid)
+
+        if not em_component.check():
+            create_fails = RuntimeError("After creation the component self check fails")
+        
+        if not create_fails is None:
+            raise create_fails
+
         return em_component
 
     ## Delete a component