Hygiene: Cleanup cookie usage in MobileFrontend

use jquery.cookie
Kill test which is not useful.
Also remove unused removeCookie method.
Add deprecation FIXME to remove these in future

Change-Id: I7e385ad0fa6e12e8c5653f1e9e4b5634ea07ab77
Merge "Hygiene: Cleanup cookie usage in MobileFrontend"