BlinkyTape: firmwareName and maxBrightness should be part of scene

[cibomahto]

For expediency, the firmware name and brightness are being stored as global parameters:
https://github.com/Blinkinlabs/PatternPaint/blob/master/src/app/gui/mainwindow.cpp#L1212
https://github.com/Blinkinlabs/PatternPaint/blob/master/src/app/gui/preferences.cpp#L30

The scene template should kept around by the main process, and these parameters should be stored in it instead.

[cibomahto]

This would also allow us to implement the different matrix types