Mulgara

To provide a simple administrative routine, it would help if the resolver interface supported backup and restore capabilities.

This will allow resolvers to also dump their data into a backup, and have restore data brought back in. This will only be applicable to writable resolvers.

Resolvers may also need to mark a new section of the backup file, which will be ignored by other resolvers. This will result in new code that asks each resolver if it can do backups, and during restore it will need to iterate over each resolver to find out with one can handle the data about to be restored (according to a section marker in the backup file)