support creation of OS X framework bundles

To create a framework bundle, set your product type to
"frameworkbundle". The bundle creation is similar to the
"applicationbundle" product type.

Task-number: QBS-274
Change-Id: I103feb59e141c463f66ebb45f08cea61dad5d880
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>