Take care of unclean shutdown with Ctrl+C KeyboardInterrupt

[dspruell]

$ sudo ./venv.d/ampt-generator/bin/ampt-server 
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
^CError in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/popen_fork.py", line 29, in poll
    pid, sts = os.waitpid(self.pid, flag)
KeyboardInterrupt

A couple of exception handlers for KeyboardInterrupt have improved the situation, but need to figure out how to address a keyboard interrupt causing a messy looking traceback on exit.

Possible resources:

• http://jtushman.github.io/blog/2014/01/14/python-|-multiprocessing-and-interrupts/
• https://stackoverflow.com/questions/11312525/catch-ctrlc-sigint-and-exit-multiprocesses-gracefully-in-python
• https://stackoverflow.com/questions/21104997/keyboard-interrupt-with-pythons-multiprocessing