two layers, X and Y oriented, filament saver, bed leveling thing

Hi,

This work is based on http://www.thingiverse.com/thing:10402 from woodsmoke.
I used to use it for fine bed leveling calibration but it had two things missing for me, so here is a redesigned version of the same concept with, in addition and for our pleasure :

• Two layers thick. Just to make sure the first layer is indeed a bit squeezed and the second not, and layer alignment is fine.
• X and Y orientation, just to make sure you don't have (as I had) an X or Y mirroring problem.
  Have fun !