check if a proposal title is a valid variant name
check if a proposal title is a valid variant name

This is important because proposals may create variants with
the same name later on

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