(group of pull requests) PR-all-auto: All those little PRs merged into this big one to see the whole picture

[SebastJava]

Closes #374

• Quickly and easily update colors. Because you can change your mind at any time and because color trends are always evolving.
• Open the doors to some small application that would empower people to create their own color variations.
• Make things much easier for all those people making forks or clones from mint-themes.

Complete story: https://github.com/SebastJava/mint-yz-theme/tree/PR-all-auto#readme