UPdate ets_fiberalloc to output pfsDesign FITS files

To my understanding, ets_fiberalloc is supposed toi output pfsDesign files in FITS format. To achieve this, I plan to

• have ets_fiberalloc import pfs.datamodel for easy creation of these files
• put all information I have currently available into these files.

But there are large parts of the file, like "tract", "patch" and everything flux-related, which I can only fill with dummy values.