Beta Casted Prusa parts

This is a derivative work of the original Prusa 3D printer (http://www.thingiverse.com/thing:4148).

The idea of metrix labs' pourable clonedel parts was good, but the parts have some technical shortfalls.
So I changed some parts into a pourable and working Prusa 3D printer.

This is the result:

The parts are like a standard reprap Prusa Mendel 3D printer. Most of the parts are pourable just the way they are. Only a few parts have too long holes inside or the walls are too thin - these p