ZP-249 #comment Mark a state as "used" for heartbeat when data is imported. Heartbeat should return an invalid state when an imports happenes on an observed folder. #time 3h

git-svn-id: https://z-push.org/svn/z-push/trunk@1557 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5