Changes to the ported PS41 global suite to run UM at N640

• The CX background files are bigger: an N640 CX background is 4 times bigger than N320. This means memory requirement of gl?_ops_process_background_* tasks increased by a factor of 4. However Ops_ExtractAndProcess tasks fail as each of the processes seem to run out of memory.
  • It turns out that the namelist variable, sharememory is set to true; this was changed to false