Allow ACL import from JSON

[dictvm]

ACL rules are pretty complex to write by hand - though maybe I'm just doing it wrong. So far I have not found a tool that makes it easy to create ACL rules. It would be useful if consul admins could simply write rules in prettified JSON, save them to a file and import it using a syntax similar the that being used to import key/value entries:

key/value:
consul-cli kv create --json kv.json
acl:
consul-cli acl create --json acl-rules.json

This way, admins could pull a list of all ACLs, save them to a JSON file and import them again using the same tooling:

consul-cli acl list >> acl-rules.json