Customizable OpenBeam End Cap

This is an end cap/foot for OpenBeam (so your skin does not meet sharp aluminum corners), with added extensions to help stabilize the beam on the table (so it won't easily knock over while working).

3 STL versions are included: a plain end cap with no extensions, an extra strong version, and a reduced material version (useful when using certain powder binding and resin jetting printers).

This is part of a system of designs that turns an Open Beam into an optical rail. An optical rail is a long, straight, sturdy rail onto which optical components such as light sources and lenses can be bolted down and easily shifted along the length of the rail.

Commercial optical rail sells for $250+/m. Open beam only costs $12/m for the fancy black anodized stuff. You get the idea.

This component is inspired by the [Open-source optics project](http://www.appropedia.org/Open_source_optics), whose goal is to radically reduce the cost of scientific optical hardware, by the [Michigan Tech's Op