Do not display a folder below the Groups if the files are in the same
directory as the product definition.

The product directory is chosen since the groups can be implemented
elsewhere as done in creator for the pluginspec groups.

Task-number: QBS-257 (partial)
Change-Id: I0e39bbc62f991f2485adb3c4b47dd62dfa72763c
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>