printedparts stage 1: scaffold, no AssetType, manifest per spec

flask plugin new output, minus the scaffold's AssetType seeding:
printed parts are quantity-based consumables, not ADR-001 assets.
on_install seeds the three plugin settings instead. Manifest pins
core >=0.11.0, depends on employees (badge name resolution), ships
disabled until a site opts in.

plugins/printedparts/models/__init__.py

@@ -0,0 +1,5 @@
+"""Printedparts plugin models."""
+
+from .printedparts import Printedparts
+
+__all__ = ['Printedparts']