Configurable appearance

Origin gen/engineering.yml 9:5
Uri engineering://nasdanika/modules/engineering/modules/gen/issues/appearance
Target Generation Adapters
Showing/hiding/placement - child, navigation, section, .../styling - icons. Perhaps appearance model and not specific just to engineering, but generic and handled at EObjectActionProvider with extensibility. References with eKeys shall make it easy to build such a model - class(ifier) and feature keys. More complex with operations, but it is an edge case. Modal actions. Cascading appearance. Ability to define Bootstrap appearance - extend? Custom properties, e.g. to show/hide columns in issue tables.