Add support for i18nSplit combo config property

Setting this property will cause the aggregator to split aggregated requests into i18n and non-i18n requests.  This will allow greater reuse of non-i18n responses in public caches.
It's not necessary to check fore URL length limits if we enter enter the code block because the length check will be done below, assuming that we exit the code block normally.  If we return from the code block, then the length check will be performed in the recursive call to sendRequest before the request is sent.