746 migration

note quite done. Still have to add the flagging that a shard has been migrated so it won't be done again.

I'm also considering making data migrator only run if they start up influx with an argument to do it. That way, people could upgrade, start things up and then create shard spaces before migrating data. Thoughts?
We shouldn't be parsing queries over here, we can just use the coordinator.RunQuery() to do all the parsing and query logic. This is a one time thing, but encouraging code reuse is good especially if this piece of code was used somewhere else.