Some cleanup of the property statistics code

Also removed the triggering of the update from the setup code which is called on every update.php and added a maintenance script to just trigger the rebuild.

Change-Id: I2e509e08663186afe116ab5db4f110ace4295b4b
Added MessageReporterTest

Change-Id: I634c0db73519c1760b6982b0b5b3ce7120ec3ecb
Added PropertyStatisticsTableTest

Change-Id: I7c7bf6398b140b5b93bdde6a9c1933404c0f7c3f