[ajax js/css] modconcat fix: load code exactly once (auc, fcayre) * introduces cw.ajax namespace (currently hosts only recent modconcat functionality) * handle load-one/load-many-at-once edge case * properly handle already-loaded js resource * avoid .appendTo to trigger script evaluation since from jquery 1.5 this results in uncached ajax calls

debian/tmp/usr/bin/cubicweb-ctl usr/bin/
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/cwctl.py usr/lib/PY_VERSION/site-packages/cubicweb
debian/cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl