[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
Experiment with the search bar. Try queries like "card sometextualcontent" or
"card wikiid index" or "345".