RA-379: Persist User session location

Added FragmentController to persist user session location
Corrected header.gsp to call SessionFragmentController
Since this method now has the side-effect of writing through to the session, you should also do a PR to get rid of some code in openmrs-module-referenceapplication that doesn't need to do this anymore:
https://github.com/openmrs/openmrs-module-referenceapplication/blob/master/omod/src/main/java/org/openmrs/module/referenceapplication/page/controller/LoginPageController.java#L153