gtexpcube: LONPOLE and LATPOLE header keywords are incorrect

[jasercion]

Porting over STGEN-110. Opening this as an Astro package issue as that is where Jim identified the coding issues at fault.

The coding error is in astro::SkyProj::setKeywords:

// todo: fix these
setKey("CROTA2", 0, "", "Image rotation (deg)");
if( std::string(m_wcs->ctype[0]).substr(5,3)=="CAR") return;
// these may be needed by ds9 for non-CAR. I get confused
setKey("LONPOLE", 180.0, "deg", "longitude of celestial pole");
setKey("LATPOLE", 0, "deg", "latitude of celestial pole");
}

http://glast.stanford.edu/cgi-bin/viewcvs/astro/src/SkyProj.cxx?view=markup