Add IGN France geocoder support, an XML based geocoder where we translate results to json objects

Change to manage correctly unicode in ElementTree for all Python version

Changes to use None instead of empty strings and correct query as a required argument

Manage when adding IGNFRANCE_REFERER in tests for ignfrance. It was revealing an error in the main ignfrance.py code

Refactoring for request part when using referer auth. Make 'query' required and remove the test for 'query'. Add deserializer to manage API that do not rely on JSON

Remove self.scheme because already provided by super, line 69

Remove sel_pl_attr function to use string format instead

Correct None for downstream and manage xml_request as a class variable

Complete documentation to match the args numbers in various ignfrance.py methods

Remove reference to encoded string in documentation

Fix regression when managing cases with REFERER or with couple USERNAME/PASSWORD
Integrate IGNFrance