yield error on invalid FileTagger items

Change-Id: Ibf8817caffe00e2b5178fa1e53dfae4d5c5c64c1
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Add new XFAIL autotest for property change tracking.

Change-Id: Iadc3bad09b4643151d8adf54a7850a8dabbd49f2
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>