Description of feature

At the moment the number of running processes can be changed only using ps:scale which restarts the app with the newly specified number of processes.
Sometimes we need to increase the number of running processes without restarting the app, not only because restarting is slow but there might be long running workers which get killed by the restart.
Therefore we need a way to increase the number of running processes for a specified type of process without restarting the app.
The existing processes would not be touched. Just start new processes of the specified type.

Please let me know if you need clarifications.