Upgrade file format for forestDB after upgrade from 4.0 and 4.1 in GSI

TL;DR
We need to trigger a full compaction at the time of upgrade from 4.1 and 4.0 to 4.5 in the index service and document that only after the full compaction is done that users have the ability to switch to circular reuse.

Details:
When users upgrade from 4.0 and 4.1 to 4.5, the default compaction option is triggered by fragmentation % (30%). However users can change the compaction trigger method from % frag. based trigger to circular reuse with time triggered full compaction. If they do this quickly after the upgrade, there is a chance that full compaction may not have kicked in and file format is still the 4.1 file format for fdb. In this case, circular reuse does not work correctly. we need to upgrade the file format at the time of upgrade to minimize chances of users getting into this state.