Merge pull request #49 from AxTheB/master

New Y belt holder
Merge pull request #50 from AxTheB/master

Mirror xends so the nut traps are on top
Merge pull request #51 from AxTheB/master

Add sample STLs
Merge pull request #52 from AxTheB/master

Allow Z bearing holder to grow for lm10uu/lm12uu bearings
Merge branch 'master' of github.com:josefprusa/Prusa3
More sample stls