Database migration questions

[abbottdev]

Because Redis.OM does not support migrations at this stage (nor may it ever) - we need the ability to be able to idempotently tell the state of an index based on the currently defined class types.

The code for this exists already in Redis.OM, I believe we should make it public so that consumers can compare the index state to their own state.

I've drafted a PR of what I think this needs to look like, would love to get some traction on it: #479