P3Steel lasercut version 2.01

This is the same 3mm steel structure as the original P3Steel "Leonardo" by Irobri, version 2.0, with a few small changes listed below. This is why I am bumping the version to 2.01.

__There are no other changes apart from those listed below:__

- The interference between the Y stepper and the M3 nyloc nut holding the Y stepper support has been solved by stretching the support by 2mm.

- The frame has been stretched by 9mm, _meaning the Y-axis 8mm smooth rods should now be 350mm long_ (same as the original Prusa i3), and not 341mm long anymore (4mm have been added to the front and 5mm to the back).

- Two 3mm holes have been added along the sides of the front Y-axis subframe, one on each side.

- The almost useless part that could eventually be used as a Y belt holder has been deleted (there are much better designs that can simply be printed).

There are no other changes because imho the original P3Steel design is already practically perfect. Thank you Irobri for this awes