adds a bash script that uses exec or bash -c to execute to command arguments
adds a bash script that uses exec or bash -c to execute to command arguments

* child process will be started as background process and receive the same signals from the parent process
** SIGHUP SIGINT SIGQUIT SIGTERM SIGUSR1 SIGUSR2

* child process will be terminated after 5 seconds forcefully

* logging can be activated using a debug=<non-empty> flag

NOTE

> https://docs.docker.com/engine/reference/builder/#entrypoint
> https://github.com/lgierth/docker-exec/blob/master/docker-exec
> http://stackoverflow.com/questions/9256644/identifying-received-signal-name-in-bash-shell-script

refs #2

encodeering/docker-debian