WIP tiered index.

Change-Id: Iae0aa792236b145a61110ab9508c6d79831fd366
WIP more tests

Change-Id: Ie7d1a2276637d1b435a94693542fc9bb36d2c05b
TIERED INDEXES CHECKPOINT.

Change-Id: Ie1ce5d7fea12b58dfd594529f9052db172525acf