Django 2.0 removed `django.core.urlresolvers` (which was
replaced/deprecated in favor of `django.urls` in 1.10).
Django_nose is also needed to run tests.

This unifies the way we parse xml server side and client side.

Related D396#inline-1961

This takes care of current limitations:
- duplicated elements are stored as list (and no longer dropped)
- drop extra namespace in key names
- it's generic

Close T1131

Related T882

Related T919

Also remove unused dependencies