Update: implement with pid execution, simplify related rules.

Update: implement with pid execution, simplify related rules.

Implement the with pid execution.
This expects the process to be spawned in the background.

After some review, I decided to remove "use" and "create", replacing those with "pid_file".
The reasons are:
- For "use", the spawned service manages the pid file, so it would be overly complicated to try and manage it in addition to the spawned service.
- For "create", if the process is to go into the background, in order to manage it then there would still need to be a running process (this defeats the purpose).

When the termination signal is received, then inform any background process spawned by the controller program to exit, based on the existence of the pid file.