Cross-nomenclature mapping is incorrectly labeled.

The cross-nomenclature widget is incorrectly labeled and underspecified. We need to add some helper text or description of the widget. I think it's going to be difficult to communicate to others what is going on here.

Please update text and mappings to:
subheader text: Provisional mapping of possible relationships between cell types across publications.

Column one:
Header: Relationship
show displayLabel for predicates: TEMP:mapsTo, TEMP:assertedSubClassOf

Column two: Cell Name
show localLabel for the object of the triple from column one.

Column three: Source
show displayLabel for DOI. else, DOI.
this is impacted by #187 ; i'm assuming author, year will be the displayLabel, but Tom will clarify.

remove Column four