Add an initial_schema option

Just like the initial_token option, we can have an option that lists the initial schema we want a node to read.

This comes in handy in situations where multiple nodes have schema disagreements, even if split between 2 or more schemas.

This can be a hidden option, but would be nice to see in rare cases, especially since I've been noticing that schema disagreement resolution has been taking more than one round of restarts lately.