Fix Ctrl+C handling in CLI
Fix Ctrl+C handling in CLI

Ctrl+C was not being properly handled by the CLI, resulting in an  unclean
shutdown and other unexpected consequences -- e.g. a
"./start-mycroft.sh debug" would kill the background processes on exit.  The
KeyboardException was never being triggered.

Now the SIGINT is being captured and Ctrl+C behaves (as intended) just like
pressing Ctrl+X.

linuxipho/mycroft-core,linuxipho/mycroft-core,forslund/mycroft-core,Dark5ide/mycroft-core,MycroftAI/mycroft-core,forslund/mycroft-core,Dark5ide/mycroft-core,MycroftAI/mycroft-core