[eclipselink-dev] Persistence Unit Composition wiki doc

[Andrei Ilitchev <andrei.ilitchev@xxxxxxxxxx>]

Added Testing to the doc.
http://wiki.eclipse.org/EclipseLink/DesignDocs/328404_new#Testing

It describes where the tests are and how they organized.

The tests is a good example how composition is setup and used.

It could be useful to compare the new composite tests with the 
corresponding original ones to see the differences and limitations of 
composition.

Thanks,
Andrei