Fix id bug with empty hierarchy root node

Fixed issue #81. A unique id is assigned to the root node now.

Change-Id: Ib732fc46a4288f2a6c19ba182b5c87e6cfe7fa20
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Remove unnecessary information message (issue #80)

Change-Id: Ie6f6c1e4f2d455cdc7ccfae362dae557c183620b
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Merge pull request #83 from DenisKnoepfle/master

Fix #80 and #81