added 'deci-mils' and 'deci-mil' to unit conversions
czone needed min_thickness, not width (bug fix)
hack: added font file to be passed in on command line for brdgerber.py
shape_code needed to be converted to string in jsonbrd.py (bug fix)
no shape for lable in jsonsch.py (bug fix)

arcs still need work in brdgerber.py