implement proper responsiveness for various devices
(it previously wasn't quite right)
remove old debug code
some minor style adjustments
version 2.3.2-exp.15 made ManageSessions class more self-contained
(makes for cleaner code)
- added global exception handler
- moved manageSessions operations to be fully within the class.
- eg. load and save are handled as necessary with the class.
- remove last last of the deprecated code from enrol.php
- changed Sessions Class to be ManageSessions Class
  (now it matches the fill name!)
- made manageSessions sort function static
NOTE. Still not doing file locking
Silently reject empty username login attempts
+bugfix on exception handler - now using quoted string for fn name.