Add RebuildPropertyStatisticsMaintenanceRegressionTest

- Caught Fatal error: Declaration of SMW\SQLStore\SimplePropertyStatisticsRebuilder::rebuild() must be compatible with SMW\Store\PropertyStatisticsRebuilder::rebuild(SMW\Store\Store $store, SMW\Store\PropertyStatisticsStore $propStatsStore) in SimplePropertyStatisticsRebuilder.php on line 23
- Caught Fatal error: Call to a member function freeResult() on a non-object in SimplePropertyStatisticsRebuilder.php on line 85