[Section] Add create_section method

Author: mpsonntag

odml/section.py

@@ -582,3 +582,17 @@ def reorder(self, new_index):
                              "Section has no parent, cannot reorder in parent list.")
 
         return self._reorder(self.parent.sections, new_index)
+
+    def create_section(self, name, type="undefined", oid=None):
+        """
+        Creates a new subsection that is a child of this section.
+
+        :param name: The name of the section to create.
+        :param type: The type of the section.
+        :param oid: object id, UUID string as specified in RFC 4122. If no id
+                    is provided, an id will be generated and assigned.
+        :return: The new section.
+        """
+        sec = BaseSection(name=name, type=type, oid=oid)
+        sec.parent = self
+        return sec