Add mechanism to notify user that Inventory skipped some object data lines

[bskinn]

For malformed inventories... probably only ones custom-created, rather than Sphinx-generated... otherwise objects could mysteriously vanish on load.

Ed: Noo, there are some Sphinx-generated inventories that load oddly; and, there are some inventories that newer versions of Sphinx don't import every object from. Notifying of that miss on both sides could be valuable.

Probably want to integrate into both API and CLI.