Dev Log #41 - Envelope editor improvements

The envelope editor is now fully reimplemented and I added lots of improvements. The most obvious ones are:

• An "Enabled" toggle in the bottom right which allows you to disable the envelope without clearing the points.
• An "Always Visible" toggle as demo'd in the video
• Points can now be selected by left-clicking on them and an x/y editor will appear in the footer for precise editing of points.
• Points now always snap to micro-increments when appropriate (usually it's 1/10th of the parameter's display unit) so for example a pitch value like 12.11458 will snap to 12.1
• Values are now always displayed in a format relevant to the associated parameter.

I also added some "quick select" hotkeys (by default the numbers 0-9) to select from the active modulators of the hovered block.

The really nice thing from the development side is that nothing is hard-coded anymore. The envelopes are all declared by the sampler plugin and Blockhead just automatically generates controls for them.

The plugin can even declare additional controls to be shown while an envelope is being edited, as is the case with the "Noise Mode" option in the video. I added a noise generator to the Classic sampler to test this which I will probably keep, though in the future effects like this will usually be implemented as separate effect blocks.

The process of adding the noise generator was very fast thanks to all the groundwork now in place. The associated parameters are added by more or less just populating some structs in C++. The data required by the DSP is then automatically formatted by Blockhead into a way the plugin understands. The eventual effect system will more or less be using this same mechanism so hopefully I'll be able to re-implement the effects pretty quickly.

I'm currently finishing up some small UI tweaks to the envelope editor and next up I'll probably start working on re-implementing Fudge using the new plugin API, and the API itself still requires a bit of work to make Fudge possible.