Drop most of deprecated code
As in previous changesets, most code has been deprecated since a very
long time. This changeset concerns "core" cubicweb modules
(e.g. "server", "appobjects") for which it's not easy to handle change
atomically.
In cubicweb/server/querier.py, we adjust empty_rset() function as a
result of "rqlst" argument of ResultSet being dropped. (There was no use
of the keyword argument anyways.)
