Authentication in the UI

[sampsyo]

This is my first attempt to obviate the need for CLI tomfoolery to authenticate with the LG API. Home Assistant's "configurator" can prompt the user to go to the login page and to paste the resulting authenticated URL.

Things still to do:

• We still require a country and language to be specified in the configuration before the authentication will work. We should prompt for those first. Unfortunately, that means it's a two-step process, because the login URL depends on the language and country.
• Use configurator.request_done to mark the interaction as complete once we have the URL.

Any help would be appreciated!