Implement color themes

[Jon Evans]

Users should be able to switch between sets of color options (themes) in all programs. Ideally these themes should be stored as files that can be shared / backed up / checked in to source control if desired. Part of this is a refactoring of the color settings code to be unified among all the programs, and clean up some aspects of color handling when switching between legacy and GAL canvases. This will also enable a "reset to default colors" option, in the form of a "KiCad Default" theme that cannot be overwritten.

[Thomas Pointhuber (pointhi)]

I made a repo with some example color schemes: https://github.com/pointhi/kicad-color-schemes

[Michal Lukowski (woocom)]

Hi
Here is my final solution:

Eeschema: fully working color scheme - candidate for release

    Added:
    - Changing color scheme from choosing list
    - Restoring the default colors by selecting "Default" from the choosing list
    - Importing color schemes from an external file
    - Create a list of color schemes to import from a file with multiple
    color schemes
    - It is possible to choose schemes from the list to import
    - Exporting color schemes to an external file
    - Create a list of color schemes to export
    - It is possible to choose schemes from the list to export

Attachment contains patches, color schemes to import and screenshots

Link to my github: https://github.com/michallukowski/kicad_my_features/tree/color_scheme

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2057