Allow KP-6 Keypad Presets to Act as Source Selection

By default, on the Autonomic KP-6, the numbered preset buttons (Buttons #1 through #4) act as Presets.  In some installations, it may be desirable to have these numbered buttons select a Source rather than a Preset.  

To configure the Keypad to toggle between Source and Preset modes, connect on port 23 (MMS) and use the command KP6SourceSelection true|false

KP6SourceSelection true turns source selection on.

KP6SourceSelection false turns source selection off (defaults back to preset mode).

When in Source Selection mode, a short press on a numbered button will switch to that source. Sources 5-8 are accessible with a long press. For example, a short press on #2 switches to Source 2 while a long press on #2 switches to Source 6.  Selecting a source which doesn't exist will always revert to Source 1.