Remove invalid JSON character escaping

These 4 lines were added 4th April 2012, but escaping `'` characters violates the JSON spec. If the server side sends a RAW containing an escaped `'` character, the client side JSON.parse in apeCore.js throws an unhandled exception and breaks the APE application in the browser.

The original intention seems to have been a fix for the JSONP transport.  So if this is still required it should only apply to JSONP and not globally.