[INTERNAL] moved consistency watchdog server component into session
scope

Also made some modifications at the class itself. 

No longer uses Eclipse Jobs.
Better cleanup, DocChecksums are now disposed on component stop.

Change-Id: Id79518638356a29d23e3c36b58b04ef9e51f7fec
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1392
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>