fix history link for variants in PageController.show()
fix history link for variants in PageController.show()

Generate the history link for the the variant text object, not the page object.

alkadis/vcv,DanielNeugebauer/adhocracy,DanielNeugebauer/adhocracy,DanielNeugebauer/adhocracy,liqd/adhocracy,alkadis/vcv,liqd/adhocracy,phihag/adhocracy,DanielNeugebauer/adhocracy,DanielNeugebauer/adhocracy,SysTheron/adhocracy,alkadis/vcv,alkadis/vcv,alkadis/vcv,phihag/adhocracy,liqd/adhocracy,phihag/adhocracy,SysTheron/adhocracy,phihag/adhocracy,phihag/adhocracy,liqd/adhocracy,SysTheron/adhocracy