Big Bearing Bear X-Axis end

Big thanks to @pekcitron and @zbrozek.
Remixed for larger (MF148) bearings and an 8mm shaft. I'm using the printed shaft included, but it really should be replaced with a metal version. The idler insert is 1mm larger, so if it's not tucked in enough the X-axis travel could be reduced.

Marked as Work In Progress due to the Alpha nature of the Bear X-Axis parts.