Fix copy chidren by abandon of recursive strategy

tracim/tracim/lib/content.py

         new_parent: Content=None,
         new_label: str=None,
         do_notify: bool=True,
-    ) -> None:
+    ) -> Content:
         if (not new_parent and not new_label) or (new_parent == item.parent and new_label == item.label):  # nopep8
             # TODO - G.M - 08-03-2018 - Use something else than value error
             raise ValueError("You can't copy file into itself")
             content.revisions.append(cpy_rev)
             DBSession.add(content)
 
-        # TODO - G.M - 15-03-2018 - Child copy broken !
-        # INFO - G.M - 15-03-2018 - copy childrens (comments and others things)
-        # for child in item.children:
-        #    self.copy(child, content)
-
         # INFO - GM - 15-03-2018 - add "copy" revision
         content.new_revision()
         content.parent = parent
         }
         DBSession.add(content)
         self.save(content, ActionDescription.COPY, do_notify=do_notify)
+        return content
+
+    def copy_children(self, origin_content:Content, new_content: Content):
+        for child in origin_content.children:
+            self.copy(child, new_content)
 
     def move_recursively(self, item: Content,
                          new_parent: Content, new_workspace: Workspace):

tracim/tracim/lib/webdav/sql_resources.py

         )
         workspace = self.content.workspace
         parent = self.content.parent
-        self.content_api.copy(
+        new_content = self.content_api.copy(
             item=self.content,
             new_label=new_file_name,
             new_parent=destination_parent,
         )
-
+        self.content_api.copy_children(self.content, new_content)
         transaction.commit()
 
     def supportRecursiveMove(self, destPath):