Add hapic debug mode feature

tracim/__init__.py

     # set Hapic
     context = PyramidContext(
         configurator=configurator,
-        default_error_builder=ErrorSchema()
+        default_error_builder=ErrorSchema(),
+        debug=app_config.DEBUG,
     )
     hapic.set_context(context)
     context.handle_exception(NotFound, 404)

tracim/config.py

             '604800',
         ))
 
+        self.DEBUG = asbool(settings.get('debug', False))
         # TODO - G.M - 27-03-2018 - [Email] Restore email config
         ###
         # EMAIL related stuff (notification, reply)