Close project property windows when unfolding t4 templates

#378 

Eagerly closes the project property pages which might cause a code generation exception. A single notification is shown if pages are to be closed.

This workaround will iterate over all open windows for each template that is unfold. It will no longer be needed once NuPattern can deal with this exception.

Related NuPattern Issue: https://github.com/NuPattern/NuPattern/issues/2