[sakai2-tcc] Filtering Content served from CHS

[Matthew Buckett]

http://jira.sakaiproject.org/browse/KNL-629

Does anyone have any objections to this going it.

It allows filters to wrap up the output stream which means that can
change the content (add head/tail, compress, etc).

There's another half of the patch which is a simple change to
Resources to allow users to control this.

--
  Matthew Buckett
  VLE Developer, LTG, Oxford University Computing Services