Update shard space to not set defaults

Fixes #886. Shard spaces would not have compiled regexes when the server is restarted and the cluster config is pulled from a raft snapshot. A call to MatchSeries would then reset the regex for the shard space. BAAAAAD.
Add ability to update existing shard spaces.

This will help users recover from #886. It's dangerous functionality because it only changes the metadata. Will document and tell people to use with caution.