Make Obsolete inheritable by it's children in a Class Library

When setting Obsolete on a top level of a class tree all of it's child classes should be set as 'Obsolete' - WorleyParsons/GTC

If a customer is working with a large master Class library which has Classes and Structures not required by every type of project they will want to make certain classes obsolete - and therefore not usable in a specific project.

If you make a Class which has children obsolete - this is not currently inherited by its children. these means that:

1. The children will remain active until you manually make every child obsolete

2. Depending on the level this parent it might have a large number of children - meaning the best way may be to export into excel make the changes and upload

3. The user can't be certain that all children are obsolete until validation is run and succeeds

All of which is a time consuming process and can be resolved by inheriting the Obsolete property within the class structure