Eventually we will want to use this code in other sample applications,
so let's move the logger configuration code to a separate function.

There's a bit of ugly hacking in this current implementation because
I've added variable members to logging.logger.  These are actaully
config-once variables that convey the logging directory and filename.
I did not want to add more names to the global namespace, so I hacked
a temporary solution in which logging.logger is acts as a conveyor and
private namespace.  We'll get that cleaned up as we do more refactoring.

This is a niche feature, which lets you print the names of the modules
in a model, from the command-line.
Non-leaf nodes are excluded from this list.  Other caveats are documented
in the code.

Data parallel models may execute faster on multiple GPUs, but rendering
them creates visually complex and illegible graphs.
Therefore, when creating models for a PNG summary, we opt to use
non-parallel models.