as we have an API for restore a keyspace / table, let's expose this feature
with nodetool. so we can exercise it without the help of scylla-manager
or 3rd-party tools with a user-friendly interface.
in this change:
* add a new subcommand named "restore" to nodetool
* add test to verify its interaction with the API server
* update the document accordingly.
* the bash completion script is updated accordingly.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
03ab80501f