Added ServiceLabelIndex Characteristic, which seems to be required as noted in HAP specifications. However, linking to a ServiceLabel Service does not appear to be required, so there is no need to build any Service-Linking logic into homeSpan - will wait for use-case to be identified.
To do: Add support for double-click to SpanButton, then include in Example 16.
Modified SpanCharacteristic::sprintfAttributes to streamline logic and add special handling for the ProgrammableSwitchEvent Characteristic as required by HAP: the value returned for the database or any read request must be set to null (i.e. "value":null). The only time the real value should be returned is when the device sends a EV/Notify message (when the button is pressed). Verified that the example works as expected!
TO DO: Add functionality to allow for Service Namespace and Index label so that you can have multiple programmable pushbuttons in one service - this requires logic for HAP LINKED SERVICE functionality.
Gregg