Enable alternate color palettes and output formats

[sarahec]

Building on #15, we'd be able to include implement svut_h.sv as a group of header files.

Why? I've prototyped a very nice color palette system (that uses a header file to define colors, another to define the palette (e.g. dark mode, light mode), and then the SVUT test macros.) While dark screens are all the rage, we also need to think about people who still work on white backgrounds, people who cant work with color (e.g. because the contrast is too low or due to colorblindness), etc.

This would also allow plugging in alternate output formats (Markdown, HTML, etc.) trivially by redefining one macro and including it in a file before loading svut_h.sv.

Using #15, a multi-file svut_h.sv would simply have the main header file include its subsidiary header files (with a ifndef wrapper) and they could be overridden by loading something different in front of svut_h.sv.

It sounds complicated, but it really isn't. Most people will include the standard header file. Some will also load a "light mode" or "monochrome" file in front of this to redefine the color palette. That's it. Fully backwards-compatible with easy room for growth.

[sarahec]

Closing due to not having the time to pursue