Add more stats and refactor to handle more

Add an addStatistics() method to the TaskAttributeFactory to separate
out the part to create statistics for a TaskAttribute from the main
logic. Add hasUnfilterableSubNodes and nodeByBranchCache statistics to
the node level statistics ouptut, and add numberOfChangeNodes and
numberOfDuplicates to the query statistics.

Change-Id: Ie57f5d1ee2c44dabb71cee0f7f36788b7f69adb9