Introduce oauth2 device flow for users and devices

[doanac]

Implement support for oauth2 device flow that will support:

• satcli login - rather than creating an API token by hand, this can create the token
• lmp-device-register - allow a device to obtain a token with devices:create permission f

[doanac]

I have two branches that have been prototyped to do this:

• https://github.com/foundriesio/dg-satellite/tree/oauth2-flow
• https://github.com/foundriesio/dg-satellite/tree/lmp-dr-support