Allow token authentication for Hook switch component

[KlaasH]

Description:

The Hook switch component currently uses username/password to get a token from the Hook web app to use for subsequent requests. This PR adds an option to specify the token directly in config.

Makes the 'password' and 'token' options mutually exclusive since otherwise one would have to take precedence, and it seems worth preventing people from filling their config with passwords that don't
even need to be there.

Pull request in home-assistant.github.io with documentation: home-assistant/home-assistant.io#2378

Example entry for configuration.yaml:

# Example configuration.yaml entry
-  platform: hook
   token: <your API token>

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• [na] New dependencies have been added to the REQUIREMENTS variable (example).
• [na] New dependencies are only imported inside functions that use them (example).
• [na] New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• [na] New files were added to .coveragerc.

[mention-bot]

@KlaasH, thanks for your PR! By analyzing the history of the files in this pull request, we identified @fabaff, @dasos and @balloob to be potential reviewers.

[homeassistant]

Hi @KlaasH,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[dasos]

Well, I'm very happy that someone else is using Hook and Home Assistant! 👍

Just a thought though - might the token not expire after some time?

[KlaasH]

@dasos Thanks for writing this! I had been using command_line switches. This is way more convenient.

There's a manual "Reset Token" menu item on the web app, but I would assume they don't reset them otherwise. I guess I'll find out...