BMG MK3 mod for AM8

Print belt test before any "x carriege" to choose the right one for you.

• Changed BL_touch body
• Uploaded wrong fan pancake holder. It's fixed now (pancake_DissEd = Good). Sorry, my bad.
• Belt holder in x carriege keeps the design from prusa and most belts don't want to play nice with it. Uploaded a belt test to check which one works with your gt2 belt. The x carrieges are named accordingly (If your belt fits in number "2", download x_carriege2...)
• Changed body, cover and x_carriege(1,2,3) to use hexagonal nuts instead of the square ones. HexNut in the name for id. Printed a sample and all nut holes are ok. I did modified them. First ones weren't.
• For "fan holder both screws" the lower-right screw is 25mm. In case you don't use this part THE SCREW SHOULD BE 18MM, no more. - Removed due to screw colliding with radial fan
• Bltouch offset is 30mm for X and 0mm for Y. I used lee0101 design (https://www.thingiverse.com/thing:3230048) to incorporate the bltouch in mine