Improved DXF output compatibility

Changed coordinate order from [X1 X2 Y1 Y2] to [X1 Y1 X2 Y2]. Both orders are standard compliant but [X1 Y1 X2 Y2] is far more common and can be parsed linearly. Some libraries, like the python libraries dxfgrabber and ezdxf, cannot open [X1 X2 Y1 Y2] order.
Merge pull request #1015 from mermerico/master

Improved DXF output compatibility