Z Support revised for Prusa i3 hephestos with hard disk ball bearing

Z Support revised to include a ball bearing "13mm external 8mm internal" that can be obtained from a broken 3,5'' Hard disk.

Dismount the hard disk plate and extract the ball bearings (2), that's it.

v "d13": improved after a check and first print with prusa i3
v1_0: test in progress