Feature: Use dat.gui for options and displaying values

[joedf]

Example demo: https://davidwalsh.name/demo/dat-gui.php Example usage: https://davidwalsh.name/dat-gui Code repo: https://github.com/dataarts/dat.gui

Example 2: https://jsfiddle.net/ikatyang/182ztwao/

[joedf]

or maybe even winbox.js: https://github.com/nextapps-de/winbox live demo: https://nextapps-de.github.io/winbox/

[joedf]

Tweakpane? https://cocopon.github.io/tweakpane/

more alternatives to dat.gui: https://gist.github.com/joedf/9f0fb7d6a27dcf656170314f5b8ef605

[joedf]

Current progress todo in feature branch:

• [x] Advanced mode not respected on input image change
• [x] Optimize "Sampled Subregion" drawing like with "Spot Layout" for just image move&scale, no need to redraw each spot/circle, likely no need for computeResampledPreview() anymore...

[joedf]

The attached branch will also resolve the following issues either directly or indirectly:

3, #5, and #22