EditorComponent: onMouseClick() now takes callback for undo/redo
EditorComponentOscillator: Updated to use history callback
OscillatorDialogue: Now signals when change is made to frequency
Added EditorComponentBlackboxPin class
SourceOscillator: Changed base freq to 120hz
GraphicGen: Implemented generateBlackboxPin()
Simulation: Added support for external black-box pins
BlackBoxPin: Implemented
BlackBox: Implemented
ToolContextual: Updated to use component modify callback
Toolbox: Added buttons for black-box pins
BlackBoxPin: Made clickable; switches state if it's an input pin
ToolboxButtonGraphic: Graphics are now centred automatically
BlackBoxPin: Fixed inverted I/O mode on pin
GraphicGen: Fixed broken Black-box pin mapping
EditorComponent: onMouseClick() now returns whether it changed