New style color code for the primary pair diagram

Description / purpose of the changes

Preview at https://jo-pol.github.io/GroundForge/tiles including all sibling repositories (alias catalogues and help pages).

The Belgian color code uses a single color per stitch, GroundForge has buggy twist marks with this system. The new system has up to four colors per stitch.
The enumeration of stitches for the new system is a download.
Optimized loading/refreshing though Droste definitions with a large swatch can still cause a slow response.
The API page is split into several demonstrators with some how-to, intended for developers to whip up new interfaces for special use cases.
Changed flip from link to button and fixed the algorithm.
The enter key no longer executes "apply to all".
The sidebar directly links to an editable version of the help/catalogue pages (implemented for all repositories)
fixed the color green on the 1-color-per-stitch help page

@d-bl/gf