This adjusts the following:
* Systemd unit dependencies
* Location of docker daemon (/usr/bin/ -> /snap/bin)
* Default data storage location
* Configuration storage location
It allows optionally using both 'jq' and 'docker' from the snaps
provided by the Ubuntu server 18.04 installation process.
* Warn the user about NOT deleting containers
As the `supervisor` does not support creating the homeassistant container if accidentally deleted, let's warn the users before it's too late and perhaps give a bare minimum of possible ways to recover.
* Update README.md
