Re-implement the old template system

Huh. I would have imagined that templates would've been re-introduced alongside blueprints.

Support was built into the system (via a new Schematic type) but it was not fleshed out.

Templates are overall a lot easier to implement than blueprints, although they have some minor specificity. In this very case, it made more sense to start with the blueprint to get the complete thing working, and then link the bits specific to templates.