The Velux ACTIVE gateway uses `C#` rather than `c#` as the name of
the property that holds the count of accessories. Apple's HomeKit docs
suggest that properties should be case-insensitive, so update the
code to not assume the property names are lower case.
* Add binary sensor for Lutron RadioRA2 keypad buttons
Allow automations to be triggered from RadioRA2 keypads by exposing
each button as a binary sensor.
* Remove binary sensor component; fire events directly instead.
* Address comments from code review
The Envisalink binary sensor was logging events with a relative
timestamp that updated every time it polled, so even when nothing
new was happening, the event log would be full of meaningless
state changes. Modify the sensor code to use an absolute time
which stays stable when there isn't new activity.
koreth