Enhanced support for dash:propertyRole (additionnal roles)

[tfrancart]

Step 1: better integration between yasgui plugins and Sparnatural

yasGUI plugins should be able to notify Sparnatural of the property roles they need. This means that YasGUI plugins should be notified of the full Sparnatural object, probably, not only of the query and the config (?)

Sparnatural should have an API to the outside world setAutoFetchRoles(listOfRoles) that the plugins can call.

Step 2: Sparnatural will auto-fetch these roles

Based on what the plugin needs, Sparnatural will auto-fetch the corresponding properties when executing the query.
This should be made be pre-processing the JSON query before it is turned into SPARQL (see ongoing work in #592)

List of roles

• dash:KeyInfoRole (table, grid)
• dash:IDRole (table)
• dash:DescriptionRole (grid, map)
• dash:DepictionRole (grid)
• dash:GeoCoordinateRole (map)
• dash:FromRole (timeline)
• dash:ToRole (timeline)
• also dash:ParentRole and dash:ChildRole could be useful to auto-configure the tree widget