* Define textual state for connectivity device_class
Define textual state for connectivity `device_class` for `binary_sensor`.
Without this addition, a `binary_sensor` using the connectivity `device_class` is simply shown as `Off` or `On`. The icon does change but only if the user hasn't defined a custom icon.
* Change wording
Change `Offline`/`Online` to `Disconnected`/`Connected`
