Update required following commit 05dd4fc1.

Following the update of `Region_6_SHP_triplet` in commit ecfaaa91.

Better to check this before the creation of all the temporary files
and links, so the user does not have to clean them up before running
again.

Following update of libraries: NetCDF-Fortran is private in NetCDF95
and MPI-Fortran is private in EZMPI.

k would be for date index rather than number of days since 1950-1-1.

We need to update this input directory because of the change of DBF
field `date_index` to `days_1950`.

We need to update this input directory because of the change of DBF
field `date_index` to `days_1950`.

The node identifiers in Matlab use the date index in the array of
processed dates. This is not simply the difference between the current
date and the first date if there are missing dates. This means that
converting between node index in Matlab and date and eddy indices, one
needs the array of processed dates. Morever, the conversion from date
and eddy indices to node index requires a search through the array of
dates. So we do not keep the Matlab node identifier. We use k and n as
described in the documentation.

For this commit, we need to revert in part commit 68da90cd. We have to
read `date_num` from the Matlab files, and we create function
`adjust_n` to convert from Matlab node identifier to the new node identifier.

Rename function `convert_id` to `node_to_date_eddy`.

No longer useful. Replaced by `Inst_eddies/inst_eddies.py`.

New script to loop on detection of instantaneous eddies.

I could not reproduce the old run. And we need to update this input
directory because of the change of DBF field `date_index` to `days_1950`.

Makes it easier to log. This does not make more instructions because
 now we do not need to try creating `SHP_triplet/extremum.dbf`.

The bug comes from commit ce139a86.

We have to precise the suffix because we test readability of file with
`os.access` below. The bug comes from commit 41c8c5cc.

The bug comes from commit 4ff019ac.

Because we want to be able to easily read the edgelist with several
graph programs and they would not all accept the same
header. `read_edgelist` from Networkx accepts a comment line starting
with a special character. Not very elegant to put column headers after
a #. Anyway, the headers predecessor and successor are obvious for an
edge list.