Fix (again) for URMP configuration

Hopefully, this sledgehammer approach fixes Issue #7 once and for all.
Models seem to draw correctly:

- instantiated in the VAB, either as the first part or a symmetry part.
- when loading in the VAB
- when loading in Flight (on launch, or Switch to Vessel)
- when selecting Revert to VAB
Change top/bottom attach node processing

Read the values from the part's config node.  Fixes Issue #8.