Need config option to recognize custom cache bust query arg

[chuckdumont]

Jaggr doesn't include Cache-Control:max-age= using the expires server-side config property in responses that don't include a cb= or cacheBust = query arg. This is to prevent unwanted far-future caching of resources. Now that jaggr can be configured as a regular resource servlet, this is too inflexible as applications may not always have control over what query arg is used to specify the cachebust argument (e.g. ckeditor uses t=XXX). A mechanism is needed to specify custom URL patterns that will include the Cache-Control:max-age= header even if the request URL doesn't include the cb= or cacheBust= query args.