Added possibility to create empty CMDOWS object (root was missing before) as starting point.

Former-commit-id: 441c5949848fa4de6a87554045bcc87579c1c9a4

kadmos/cmdows/cmdows.py

@@ -37,6 +37,8 @@ class CMDOWS(object):
             self.root = ElementTree(element).getroot()
         if file_path and element is None:
             self.root = ElementTree(file=file_path, parser=parser).getroot()
+        if not file_path and element is None:
+            self.root = Element('cmdows')
 
     def version(self):
         """Method to retrieve the version of the CMDOWS file"""