Change to process name if the numprocs greater than 1

According to the [documentation](http://supervisord.org/configuration.html#program-x-section-values) the process name has to be changed if the numprocs value is greater than one.
At the moment this can be achived by defining the process_name manually in the right format.
This enhancement helps to auto set the process_name the right way.

Inspired by the [proletaryo/supervisor module](https://github.com/plathrop/puppet-module-supervisor/blob/de4b8856fa22de923b74acf9d4df49981600d8cf/templates/service.ini.erb#L4)