Flat pattern DXF export

Automates DXF flat pattern output files for all sheet metal parts. This eliminates the tedious task of opening and creating a DXF for all drawings involved.

Upon release, automatically DXF flat pattern output files will be generated for all sheetmetal parts. This eliminated the checking whether or not a part is sheetmetal and the tedious task of opening and creating a DXF for all drawings involved.