PDME — Misplaced Usage inheritance from SecurityClassifiable

Summary: Reference: PDM Enablers 2.7.3.2, 2.7.3.20

Problem: As modelled, AssemblyComponentUsage inherits from
SecurityClassifiable, but Usage does not. If Usage is ever to have other
subtypes (which is the only reason for separating AssemblyComponentUsage),
the other usage relationships (such as MakeFrom) might also be classified.
Usage should inherit from SecurityClassifiable, and AssemblyComponentUsage
should inherit that from Usage. When fixing this in the UML, "Classifiable"
should be properly spelled "SecurityClassifiable".