Fixed issue 19: now we use open_image()

open_image is now use almost everywhere (some places may still use
astropy.fits directly) and the pipeline can now run with THINGS images
that have not been fixed.
Fixed a problem with createConfigFileInteractive

The code referred to FUV_Pixel_Scale and HI_Pixel_Scale when it
should be FUV_Pix_Scale and HI_Pix_Scale.