Clarifies that your Home Assistant instance must be accessible from the
internet via HTTPS on port 443, using a valid certificate to use account
linking.
* Add documentation for configuring Alexa Intents AWS Lambda function
* Some clean up and SPG fixes
* Remove spurious 'Smart Home' references
* Wrap images in <p class='img'> in Alexa AWS documentation
* Only mention Duck DNS addon for https since it incorporates Let's Encrypt
* Use [text](url) link syntax rather than <url>