ZF-6121: Fix namespace propagation in App.php

Description

In App::importUrl() we set the API version for a data model class after the XML is already parsed. This causes a problem where certain XML elements end up in the extension_elements array instead of being parsed. The version needs to be determined prior to XML parsing in order to ensure that every XML element is addressed properly.

Comments

Fixed in trunk in r14489 and merged to 1-7 in r14490.