Change default image format for online astrometry from JPG to FITS

The severe problem of inconsistencies concerning the returned image orientation for several solver application was discussed in INDI Forum. "Online Astrometry" is fed with JPG, which leads to a wrong orientation angle (see my summary and Han's contribution). Unchecking the option "Upload JPG" in 'Align Options'/'External & Online Programs' has no effect, because it is not addressed nowhere. This PR changes the default format for online solvers from JPG to FITS, which produces reliable results. The option "Upload JPG" is removed. The tool tip for the different solvers is amended with a note, suggesting to use 'Internal SEP' together with online solvers to prevent long loading times in case of small bandwidth. (see Rob's answer)