Un-clusterified InchCoord

As well-meaning as the work on creating an InchCoord cluster class was, I just don't think it's necessary at this point, and too much complexity at this level.  It did prove out some aspects of how P001Model should work, so it wasn't a complete waste.  And the “formula” that was figured out for it may become useful later.

• Combined InchCoord and InchCoord_double implementations into a double-native InchCoord, similar in code and functionally the same as what existed before the cluster conversion.
• Removed InchCoord_NSNumber implementation.
• Removed unnecessary comments, pragmas, and constructs for cluster class stuff.