attach files to expenses (closes #2953926)

__pkginfo__.py

@@ -20,7 +20,7 @@
     ]
 
 __depends__ = {'cubicweb': '>= 3.10.0',
-               'cubicweb-expense': '>= 0.4.4',
+               'cubicweb-expense': '>= 0.7.0',
                'cubicweb-workcase': None,
                }