Make fixed keys programmable

In V2R1 we implemented some fixed keys to be able to be made programmable.

In V2R2 more functions can be programmed onto the FFKs. The affected phones and respective FFKs (some of them do provide an LED) are:
 * OpenStage 20 SIP: Disconnect, Redial, Call forwarding (LED)
 * OpenStage 40 SIP: Disconnect, Redial, Call forwarding (LED)
 * OpenStage 60 SIP: Disconnect, Call forwarding (LED), Voice Dial (LED)
 * OpenStage 80 SIP: Disconnect, Call forwarding (LED), Voice Dial (LED)

The following functions become available for the FFKs:
 * Hold
 * Consult
 * Conference
 * Repertory Dial
 * New feature Home button (aka Show phone screen) for OpenStage 20 SIP and OpenStage 40 SIP.

Note that the addition of Repertory Dial will be used in the US market to program certain feature access codes (star-codes) for the system supported features identified as:
 * Pick (Group Pick Up)
 * Park
 * Activate Hunt
 * Stop Hunt

The Repertory Dial capability will, of course, not be limited to just those four feature access codes and could be used to support any feature access code without further change to the OpenStage software.

Coloring: Functions released in V2 R1 and released in V2 R2.