Purge thumbnail cache on save
Purge thumbnail cache on save

- Issue MatterHackers/MCCentral#2766
Thumbnail cache invalidation leaves behind sized thumbnails

unlimitedbacon/MatterControl,unlimitedbacon/MatterControl,larsbrubaker/MatterControl,unlimitedbacon/MatterControl,mmoening/MatterControl,mmoening/MatterControl,larsbrubaker/MatterControl,larsbrubaker/MatterControl,mmoening/MatterControl,unlimitedbacon/MatterControl,jlewin/MatterControl,jlewin/MatterControl,larsbrubaker/MatterControl,jlewin/MatterControl,jlewin/MatterControl