Don't need some of the extra code for the stdin pipe for subprocesses.
Some new bells and whistles for specifying the command of a subsystem.

Commands were just run through /bin/sh directly beforehand. Things have
been updated so if no dashes are found in the name, the command is
looked for in libexec (which changes based on being in a development
directory or not).

If no command is specified, it defaults to the name of the subsystem.
This will be the common case for a majority of subsystems and should
make configuration easier and less error prone on those subsystems.