Extract SDSS field information and PSF

This workflow gathers information needed by the execution of Sextractor, Galfit and Ellipse, from the SDSS VO service. It receives as input a ascii table with 10 columns:
- Coordinates: Right Ascension, Declination
- Data of the field: run, rerun, camcol and field
- Path of the fits image.
- A value to indicate if the galaxy is barred or not. A 0 if it is not barred and 1 if it is barred.
- Path where the psfield file will be downloaded.
- Path where the psf file wil be generated.

The workflow generates paths of some files that should be provided to Sextractor, Galfit or Ellipse. This paths are generated using the path of the image as suffix, and creating this structure:
+Eliipse: which will contain the files needed to execute Ellipse
+Galfit: which will contain the files needed to execute Galfit
+Plots: which will contain the plots that will be generates
+psf: which will contain the psf files
+Sex: which will contain the files needed to execute Sextractor
+votables: which will contain the votables with the information obtained from the execution of the applications.

This workflow extract the band from the image header, and  the information about the field (kk, saturation, aa, airmass, gain) from the SDSS DR7 drfield VO service.
The psfield file is downloaded in the path provided in the input ascii table, and the program "read_psf" is executed to extract the psf field corresponding with the specific band of the image.

The output of this workflow is made up of 14 lists:
- Filenames: Paths where store files that are going to be generated (i.e. the output file of Sextractor)
- psf: Paths where the psf files have been stored.
- Band: List of bands correspondig to the image
- image: List of paths of images
- nx and ny: NAXIS1 and NAXIS2
- kk : List of  extinction coefficient values
- saturation: List of saturation level values
- aa: List of  zero-point values
- airmass: List of airmass values
- gain: List of Gain Averaged over Amplifiers values
- ra,dec: List of coordinates
- Bar: list of 1/0 indicating if the image of the corresponding row is barred or not