Use KSyntaxHighlighting::Theme infrastructure for color themes in KTextEditor
The idea:
Instead of relying on KConfig files we ship, just use the theme data from KSyntaxHighlighting.
Implementation idea:
Use the theme data as fallback for reading from KConfig stuff. If we do it that way, the editing parts of the colors/... can stay as it is, we just need to ensure we use the correct data as default values.
Perhaps Dominik can take a glance at this, if it makes sense at all.