print unused parameters

[ecoon]

At some point, it would be really nice to print out unused parameters. This would warn if there were unused options in the list (potential misspellings!)

Note that:

void Teuchos::ParameterList::unused(std::ostream& os ) const;

is a thing.

Note that it is likely more helpful to miss positives (the current behavior) than to have false positives.

[ecoon]

I'm not sure this CAN be done globally on the main plist. The reason for this is because several sublists will never be "used," only "copied and used," e.g. for domain_set:*-{eval,PK} lists

[ecoon]

Maybe a utility, e.g.

finalizeParameterList(plist_local);

could be used that only wrote out LOCAL unused quantities, and WARNED of their existence?

[ecoon]

Note that this implies that all future work should try to avoid copy-constructing PLists, instead passing around RCP<PList>. In this way, the original "global" plist read from the file will get as many things marked as "used" as possible.