Working according to position log

There is still an occasional graphical glitch with the toolpath preview,
but it doesn't seem to affect the machine position.
Added depth output and removed redundant field
Fixed some slowdowns when switching between tangent and parabolic blends
Trying more aggressive parabolic blending again
Debug output for optimization
Added optimization to addcircle but this didn't cure the dips
Fixed the optimization issue finally because the optimization was being run before the new segment was added
Fix for spindle atspeed hiccup
Fix for tangent arc issue that sam found