so we don't burn CPU cycles unnecessarily

since having the spindle running is useful for determining Z alignment

because I'm lazy and don't want to type 'u 5 mil'

Because I want to be able to type '5mil' and '.005 inch'.  Previously
'5 mil' would be rejected because 2 digits were required, and '.005 inch'
would be rejected because it wanted a leading zero.

Feature updates to align script

…line

to help protect the drill bit when drilling.  This is a non-optimal solution, since most times while milling we could lift-off at move speed, but I don't want to take time right now to sort out the code enough for that, so I'm just having it use feed speed every time, and relying on it not to take too long, since it's not very far and not that often.

This includes a couple of updates to make this not break visualize.py

Previous version of code left out the last mill step.  Oops!

Try to draw what the robot will etch out, assume a 45 degree v-bit

I thought this fixed another issue I was seeing, but it seems not to.  Ooops

previously it would set all the drill depths to spot-drill depths...

…ling work-flow incorporating suface probing and z_correction

Add alternate draw script, fix some bugs