- Make ParamWidget hold module/paramId instead of paramQuantity.
- Add configInput/configOutput.
- Add engine::PortInfo.
- Avoid calling particular events when cursor is locked.
- Add PortTooltip.

- Add Engine::fromJson which can be called without the GUI at all.
- Make RackWidget::fromJson attach itself to existing Engine state. However, once attached, they own their Engine objects (Module, Cable).
- Remove Engine thread. Now Engine must be stepped by other threads, such as the audio thread. This is fantastic because there is no longer a mutex lock every audio buffer.
	- Add concept of the "primary module", which is allowed to call Engine::step().
- Add many Module events.

This reverts commit a007a41b0d.