saved project archives can be saved again directly

The problem was that a newly saved project archive was leaving the
application in a totally different state than if it was loaded.
Thus saving it again was only possible after loading it.

refs #627

Change-Id: I43ef6b22b09ceb5a8d348478cea1a59d94dfbf75
Reviewed-on: http://gerrit.esdi-community.eu/3107
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>