Added testInheritedGetEnum (refs #3642)
addEnum() search for attribute in parent families (closes #3642)

If the attribute, on which addEnum() is called, is not found in the
current family, then search for the attribute in parent families.

Also:
- Refactored global cache vars into static property.
Merge pull request #685 from eguaj/3.2-A3642

3.2 a3642