[FIX] use subject instead of object in example … +

support not only object
remove rvl:ID from example data and mappings

use rdf:ID instead
simplify applyMappingToNaryRelation
simplify applyMappingToGraphicObject
[FIX] don#t reuse graphic objects as labels!
catch problems with missing labels
[WIP] making d3 code more robust and consider icon type