Reading and dsiplaying of JP2 files

This pull request covers some issues with reading and displaying JP2 files.  All JP2 files currently available at helioviewer.org have been tested.  MDI FITS headers report the solar radius in pixels; the fix for this multiplies that number by the scale in order to return arcseconds.  LASCO date-obs times were being incorrectly calculated.  STEREO date-obs times were not being extracted from the file header.  Also fixed a couple of the name properties so that more useful plot titles are shown when using the peek function.