Basic mode and print function

Added a mode selection menu which switches between guitar tone stacks and basic circuits (e.g. simple RC) for educational purposes.

File>Print will print the frequency response plot

Circuit panel is now a fixed size so doesn't move about if there are no pots

Fixed bug with wrong pot being hidden when pot 3 not used

NB: Update - have fixed issue with missing QT print dll. The current 1.1.1 archive attached here now includes it but no source code changes, hence not a new release