Styles mapping for deprecated / system colors

[jacekbogdanski]

Type of report

Feature request

Provide description of the new feature

Currently, system colors are not correctly recognized by CKEDITOR.tools.style.parse functions (#2923). As the colors may introduce some issues with different color among the systems where we expect the concrete one, it makes sense to create some public mapping which will convert styles to the expected. It should also allow to disable or change a mapping by the developer if needed.

Some poor mapping has been already introduced for Border style type (#2924) where windowtext is mapped into black color. We should extract this logic into separate namespace inside CKEDITOR.tools.style.

Note that this mapping is not limited to colors, we may need some other style mappings in the future, so the general method shouldn't limit itself to the concrete style property.