Parametric Angle Brackets (offset holes remix)

I downloaded this years ago. It's my standard model whenever I need a quick and effective angle bracket.

This is a modified version of the .scad that allows two rows of offset holes - similar to the brackets one finds in the stores.

See picture for an example. The new variables are:
- arm1_hole_offset
- arm2_hole_offset

Thanks to the original designer for a great design that's stood the test of time.