Add config options for conditionally stopping processes

- "min_uptime": if a process is restarted with an uptime smaller than this value,
  this restart counts as an unstable restart. If this option is not specified,
  all restarts are considered unstable.

- "restart_time_limit": if the number of unstable restarts exceeds this number,
  the process will be stopped and a message with number with restarts will be logged.
unstable stop should log number of unstable restarts instead of all restarts
remove pidFile when process dies
fix pm2.log not line-breaking properly