Allow Default Attribute to use inherited attributes

Derived templates (element and event frame) will not allow for inherited attributes to be used as the "Default Attribute". This breaks inherited analyses that use the "Default Attribute". The only workaround is to override the the attribute, which somewhat defeats the purpose of derived template attributes.

Ideally, derived templates would inherit their parent's "Default Attribute" (which can be a inherited attribute), or they should be allowed to override the "Default Attribute" with either an inherited attribute, or an attribute of their own. This would massively increase the flexibility of templates.