Aluminatus bed plate

This is a knockoff design of the Aluminatus bed plate for self sourcers.

Includes 8 copies of the SIMO mount plate for 2060 extrusions and 2 groovemount plates, hidden in the large cutouts.

Also includes mounting holes for four bed corners (from the original Aluminatus) or two centered holes in the back (for Eugene_B's 3-point mounting system, linked in the Sources)