[dbapi] Connection.load_appobjects should load site_cubicweb files as well, they may contains necessary RQL extension function definitions. Also kill some broken deprecated code in this method.

\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$