4mm filament tube clips and printhead cap for Wanhao D6

This remix of Wultz's cable clips is adapted for a larger 6mm O.D./4mm I.D. PTFE filament tube. The stock 2mm I.D. tube has quite a bit more friction than the 4mm tubes. The printhead block cap includes a reducing funnel that slopes from 4mm down to 2mm for a smooth entry into the printhead.