Support a user adding an item and getting a list of possible items to link to

[marcolarosa]

Consider the process of adding a GeoCoordinates item to the crate. There is currently no way to link that item to the root dataset directly so unless the user knows that they need to add a place and link it there (place is linked to root) they get a warning about an orphaned item.

This ticket is about adding an ability to items such that describo informs the user about that item could be linked to. So - geo coord could be linked to place - would you like to create one now? - place links to root dataset - would you like to link it now ? etc

[marcolarosa]

This is actually related to the work in #84 so it's parked for now.