Retraction seeker

# Retraction seeker

This script is a work in progress implementation of a gcode generator that directly produces test print gcode containing pillars with retraction segments between them using ranges of retraction distance, retraction speed and temperature.

The aim of this script is to iterate many different retraction settings in one print and by observing the output, one can find the optimal retraction setting in a few prints.

This script is currently targetted at my custom prusa i3 mk2.5 clone and will need changes to settings to allow usage with other printers. Thus this is not for people that don't know how to manipulate g-code or don't know the machine limits.

For people wanting to use this on their printer, I'd advise to first create a machine.json file containing settings for their particular printer. For possible keys see the generated gcode, as well as the python script itself.

Example (just a few of possible settings listed here):
```
{
"bed_size_x": 120,