Documentation on nested variables

[despens]

Some chameleon variables are nested, for instance $cmln-link-colors or $cmln-link-formats. From the documentation it is unclear how to declare these nested variables in LocalSettings.php, it would be useful to provide examples.

[malberts]

@despens will something like this be more useful in terms of documentation? https://github.com/ProfessionalWiki/chameleon/blob/master/docs/variables.md#link-formats

The underlying issue here was that the base light theme already declared an override, thereby preventing another override in LocalSettings.php. The workaround for now, if you want to use the SCSS variables, is to disable the base theme. If you're not using your own new SCSS file then this means your default theme will now be the Bootstrap default, but you can then use the variable. Not sure if that is an acceptable trade-off, however the only way to fix the current usage of $cmln-link-formats is to introduce another intermediate variable between the theme and the actual variable (similar to what I did for the grid breakpoints).

I removed $cmln-link-colors because it was never used anywhere.