chore: update cli command structure

[jrschumacher]

Manage policies within the platform.

Policy is a set of rules that are enforced by the platform. Specific to the the data centric
security, policy revolves around data attributes (referred to as attributes). Within the context
of attributes are namespaces, values, subject-mappings, resource-mappings, key-access-server grants,
and other key elements.

Usage:
  tructl policy [command]

Available Commands:
  attributes       Manage attributes [create, get, list, update, delete]
  namespaces       Manage namespaces [create, get, list, update, delete]
  subject-mappings Manage subject mappings [create, get, list, update, delete]

Flags:
  -h, --help   help for policy

Global Flags:
      --host string   host:port of the Virtru Data Security Platform gRPC server (default "localhost:9000")
      --json          output in JSON format

Use "tructl policy [command] --help" for more information about a command.

[jakedoublev]

Nice! Looks like the linter caught a couple things. Let me know if you want me to address.

[jakedoublev]

🎉