Fix adhocracy project link in footer
Fix adhocracy project link in footer

Point to github page, as code.adhocracy.de is broken due to certificate
problems.

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