Style param context versions use is incorrect

[BertBeentjes]

When a style param has multiple versions in different contexts, they are only used in the css when the style itself also has multiple versions. This is not ok.

Solution is to check for alternative versions of the style params along with checking for alternative versions of the styles; this is a bit more work, especially when there are a lot of style params. Other solution is to drop contexts for style params; computationally simpler, but functionally much less desirable.

[BertBeentjes]

There were several problems:

• class suffices weren't applied correctly to system structures (used for example to create headings in content items)
• in applying class suffices, the incorrect context was used

And a third one, that is promoted to a feature

• not solved: when a style doesn't have a version for a specific context, but the style param has, the style param is applied in the version of the backup context. This is deemed a feature. Rationale: the style is leading in what contexts it supports, not the style parameter.