Adding abort and interrupt signal handling for long running mode.

chopshop
  - added signal handler for abort signals
  - passed sigint to surgeon and nids processes

ChopLib.py
  - stored surgeon in choplib object so is accissble from chopshop
  - added handler for abort and interrupt in nids process

ChopNids.py
  - handling of abort and interrupt variables in core to exit nids appropriately

ChopSurgeon.py
  - added handler for abort and interrupt in surgeon process
  - removed longrun from surgeon_proc_list function b/c it is no longer used
    * needed to use self.long to update the variable in the signal handler
  - added stopread to self so could be set in signal handler