Move to base package to avoid duplicated code and gain better theme compatibility

Currently, this extensions layouts live in ``app/design/frontend/default/default`` and are duplicated to ``app/design/frontend/enterprise/default``. If someone uses not the default package, he would need to copy it, again.
This is very annoying.

It would be a better idea, to place the extensions layouts in the base package (as recommended by Magento) to avoid these problems.