ensure close file before rename bookmark file.
Add admin assets fix to CHANGELOG.
Update database configuration to validate shard spaces before creating anything.

Fixes #860. Update the validate method on shard spaces to optionally check if the database exists.
Add optional pausing to data migration.
Don't ever try to query or write against a shard that is closed or deleted.

Uses a RWlock so there's no global lock on writes or queries.
Update CHANGELOG.md
validate that shard spaces have a non-empty regex