SkyView GALEX GR4: Off center images fixed.

A new version of SkyView has been installed to accommodate the issues that off center GALEX GR4 images presented. GALEX now uses a special GalexExposure Image finder. This uses knowledge of the GALEX survey to find the center of the actual field of view for every observation. Specifically it looks for the AVASPRA and AVASPDEC keywords in the header and uses the pixel location corresponding to these coordinates as the center of the field of view. The center locations in the survey description file have also been updated to use the FOV centers rather than the nominal image centers.