always start purging with relative distance from center
always start purging with relative distance from center

When the purge move is long that is probably because the user wants to purge a lot,
which leads to thick purge lines, which should start farther away from the center.

Starting 2 nozzlee sizes away from the middle doesn't cut it for me.

Ultimaker/CuraEngine,ROBO3D/CuraEngine,Ultimaker/CuraEngine,ROBO3D/CuraEngine,ROBO3D/CuraEngine