Bed leveling and adhesion test

Simple bed levelling and adhesion test. It's 15x15cm, 1mm height square. With proper skirt (you can set in slic3r distance from object) you can check virtually any bed size.

How to level bed (few steps) (i3 prusa and other frame constructions)
- check levelling of the surface you keep your printer on (if it's not completely level - remember that the same difference you should see on printer)
- check level of your Z axis frame - it should be the same, as the level of surface you keep your pr