added Socet GXP header support
added Socet GXP header support

USGS-Astrogeology/ISIS3_scripts,thareUSGS/ISIS3_scripts,USGS-Astrogeology/ISIS3_scripts,USGS-Astrogeology/ISIS3_scripts,USGS-Astrogeology/ISIS3_scripts,thareUSGS/ISIS3_scripts,thareUSGS/ISIS3_scripts,thareUSGS/ISIS3_scripts