Print parent protected layers

Actually it's we don't print correctly the restricted access parent layers.

- To permit that I modify the print to allow to pass throw the Cookie.
- I let the mapserver_proxy to get the role_id (by removing the _transform_body hack).
- The map_resolution will be managed by the client part.
- Finally I don't allows to not connected user to specify role_id ans user_id.

Related to https://github.com/mapfish/mapfish-print/pull/52