Support Inheritance of MetaClass elements

Currently MetaClass does not support inheritance of any programming elements. In the future it would be useful to support this but to do that we need to have a schema for attributes so that we can determine how attributes are inherited. Are they inherited if their "primary key" field not declared in child class, are they always inherited, are they never inherited etc.

This relies on underlying support in the model (aka META-14) as well as support for a schema language and a Schema enabled MetaClassAccssor.