Enable editing of VVX450 softkeys

The Softkeys on Polycom VVX450 phones come preconfigured as "new call", "intercom", "DND" and "page". It would be good to be able to change these keys for all users in ring central to something more useable such as "company directory", "missed calls" etc.

An new call can be made by just dialling a number so this key is wasted.