Adjustable 2020 End Stop Bracket

This end stop bracket is modified from
https://www.thingiverse.com/thing:602730. It is an end stop bracket for
attaching MakerBot-style end stop switches to 2020 extrusions. It makes
changes intended to solve two problems:

* My end stop switches have seven solder joints on their backs, three of
which bumped into plastic on all the end stop switch brackets I saw on
Thingiverse, thus inducing strain and rotating the end-stop switch
outward. This modified design includes three holes in the bracket to
accommodate these solder joints, making for a much smoother attachment.

* Other end stop switch bracket designs I've seen provide a screw hole for
mounting the bracket to the 2020 extrusion that ends up being behind the
end stop switch itself. This makes it impossible to adjust the placement
of the switch after it's been installed -- at least, not without removing
the end stop switch itself. This design moves the mounting screw for
attaching the bracket to