[Feature] Vultr-cli updates

[ddymko]

While the cli works we should look to make some additions to the underlying structure to allow for the following:

• Testing
• New output types (json & yaml)
• Make use of .vultr-cli.yaml config
• Better alias for commands
• Examples for all commands

here are the resources that have been changed to the new structure

• account
• applications
• backup
• bare metal
• baremetal app
• baremetal os
• baremetal user data
• block storage
• dns domanis
• dns records
• firewall groups
• firewall rules
• instances
• iso
• load balancer
• private networks
• plans
• object storage
• operating systems
• regions
• reserved ip
• ssh keys
• users
• version
• startup scripts
• snapshot

The branch with the changes is https://github.com/vultr/vultr-cli/tree/rewrite

[ddymko]

addresses #72