Makes TestPullUpdatesApplied  use proper synchronization instead of relying on Thread.sleep()
Makes sure that the ordering of BrickElements in PersistenceWindowPool does not change while sorting.

Introduces snapshotting of the hitCount, performed before sorting, so that value remains stable
 and the Comparator does not come up with conficting results. This is to make sure TimSort
 from JDK 7 does not throw exceptions.

This is a step towards JDK 7 compatibility