Dual extruder calibration test

Use for fine tuning the XY offsets of the second extruder.

Update 2016 May 3: I've been printing quite a lot of these while working on new extruders and hotends, and the time it took to print the original got quite annoying. So I've created a mini version without the numbers. It's a little harder to use but does the job and prints in under 5 minutes. Pegs are 1mm, so if you slice with 0.5mm width you should get a sensible tool path.

Update 2016 Apr 3: I added a V2 of the test which is func