Multipage improvements:

- make updateFeedback virtual method - removing the need of several switches
- make it pure virtual so that forgotten implementations appear
- add those forgotten implementations (VCLabel, VCSpeedDial, and StubWidget in uunit tests)
- move changing page of widget's input sources from VCFrame to VCWidget's setPage - that way there is no need to look up number of input sources - they are available
- rewrite some while's to foreach's

It tested it quickly, but I'm not sure about the edge cases... I still don't understand some details of this.