Refactoring: Rasterparts have now exactly one image

...er/liblasercut/FloatPowerSpeedFocusFrequencyProperty.java

src/com/t_oster/liblasercut/Raster3dPart.java

src/com/t_oster/liblasercut/RasterPart.java

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

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

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

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

src/com/t_oster/liblasercut/examples/PhotoPrint.java

test/com/t_oster/liblasercut/drivers/LaosCutterTest.java