fix sending abort signal to chopshop

It seems that sending signals is interrupting pcap i/o causing exceptions when amount of data read does not match the amount of data sent. Replacing signals with interprocess communication.

chopshop
  - removed passing signals to child processes
  - call functions in ChopLib to stop/abort

ChopLib.py
  - removed signal handling
  - added functions to handle putting abort signal to nids and surgeon processes

ChopNids.py
  - moved raise so only called if not longrun

ChopSurgeon.py
  - removed signal handling
  - added queue to receive data
  - added queue reading to react when sent stop or abort