Simplify process of converting rasterized images into equivalent gcode instructions

src/com/t_oster/liblasercut/BlackWhiteRaster.java

src/com/t_oster/liblasercut/LaserCutter.java

src/com/t_oster/liblasercut/Raster3dPart.java

src/com/t_oster/liblasercut/RasterPart.java

src/com/t_oster/liblasercut/RasterizableJobPart.java

src/com/t_oster/liblasercut/drivers/GenericGcodeDriver.java