Some cosmetic changes were made in the pipeline to prepare it for the
public release. In particular the following:

 - The `README' file was updated to be more clear and follow the same
   format as that of the photometry and astrometry pipeline (with the
   necessary corrections).

 - A `configure' script was added to greatly simply the processing of
   setting the input directories. The version controlled
   `DIRECTORIES.mk.in' file is now the base file. After running
   `./configure', a copy of it is put into `DIRECTORIES.mk' and an
   editor is opened so the user can set them easily.

 - The acceptable version of Gnuastro was changed from the unofficial
   and not-released version `0.2.52-f620' to `0.2.51-bc56-bugfix'. The
   only necessary correction was in a single file
   (`bin/mkcatalog/upperlimit.c'), so that file is now included in
   this pipeline to allow easy correction to the main Gnuastro branch
   if it is necessary to fetch this snapshot from Gnuastro's h...