TMDM-7148: "Use RTE-RAP demo ,click relations button with exception"

Several fixes regarding reusable type handling (fix incorrect path when a reusable type is reused, especially when inheritance is involved).
Unit test updates.
Code clean up (visibility, unused/misused parameters, local variable extract).
Documentation update (validation rules).
Fix incorrect foreign key info resolution when foreign key was defined in a reusable type.
Fix incorrect behavior in column naming (when field with same name in defined in a sibling in inheritance tree).
Fix usage registration issue leading to incorrect detection of reusable types >= 2.