Add the ability to change the program's logfile owner

[BillBrower]

The default is root so when the log gets rotated the new log file is owned by root instead of the user who is running the program and the program can no longer write to the log.

[mnaberez]

There's a very similar issue for this open in #123. Let's track this over there.

Note:

The default is root so when the log gets rotated the new log file is owned by root instead of the user who is running the program and the program can no longer write to the log.

• The owner of the child log files is the user that supervisord is run as. That might be root but often is not. It depends on how the system has been configured.

• The child process does not usually write to the child log files itself. supervisord captures the stdout and stderr of the child and writes that output to the child logs. The issue described above should only happen if processes are trying to write to these same log files outside of supervisord.