XNAT-3302: Added check for null values for string returns and set to empty string instead of null.
XNAT-3326 Added project level control of PET tracers.
Move to jQuery 1.8.3 (still old, but fixes a bug with retrieving values from input fields on keyup/keydown - shouldn't create any problems, but TEST THOROUGHLY). Also some CSS tweaks and a 'sortObjects' utility function (in preparation for updated Project/Subject selector).