Organize better the directory `Input`: create sub-directories for regions.

Big change: use SHP triplets that can contain several snapshots. So
program `test_overlap` reads a single SHP triplet. The dates that
`test_overlap` should read are now specified in the input
namelist. SHP triplet directory must now contain a file named
`contents.csv`. `test_overlap` reads `contents.csv` into variables k1
and `ishape_last`. So there is no longer any need to read the number
of entities in one of the shapefiles.

For each region, concatenate SHP triplets for dates 2006/01/01 and
2006/01/02.

Read namelist from process 0 in program `test_send_recv`: it is
simpler since it is the default setting of mpiexec and I do not see
any drawback.

In programs `test_read_snapshot` and `test_send_recv`, just hard code
for now the ishapes we want to read in the SHP triplet.

`snapshot`. Also, move calls to `ax.gridlines` and `ax.coastlines`
inside function `snapshot`. These changes allow us to call `snapshot`
in a new figure.

Move `Region4/2006_01_01` to `Region4_2006_01_01` and
`Region4/2006_01_02` to `Region4_2006_01_02`.

Add a test of `successive_overlap` for a larger region, for which the
identifying numbers of the connected eddies are not the same for all
edges. Add corresponding input files.

Bug fix in main program `test_successive_overlap`.

snapshots in the same figure: useful for visualizing overlaps. So move
lines plotting a snapshot inside a new function called
snapshot and add option `--dashed`.

Remove the option `-e` of `plot_snaphot.py` and add directory argument
instead. The idea is that we now consider the three shapefiles as a
whole, they should always be alone in a dedicated directory.

Move the three shapefiles of `Tests/Input/Region_4/2006_01_02` to a
dedicated directory.

In `plot_snapshot.py`, netCDF variables for wind are now expected to be
called ugos and vgos.

Add a test for overlap of two different snapshots.

files, that make up a snapshot into a directory that contains only
these files. We hope that this will ease the handling of
snapshots. For now, this is useful in program
test_successive_overlap. So, in program extraction_eddies, create the
shapefiles in a directory called Snapshot. As we cannot create the
directory from Fortran (in Fortran 2003, it becomes possible in
Fortran 2008), we have to wrap the Fortran executable in a shell
script "extraction_eddies.sh". In the same way, read from a directory
Snapshot_old in programs test_read_eddy and test_read_snapshot and
create scripts "test_read_eddy.sh" and "test_read_snapshot.sh".

Reference the shell scripts "extraction_eddies.sh",
"test_read_eddy.sh" and "test_read_snapshot.sh" in JSON test files.

In program test_successive_overlap, finally read two snapshots, from
directories Snapshot_1 and Snapshot_2. Pass to successive_overlap the
date of the second snapshot. Use new variables corner_deg and step_deg
to avoid converting to rad twice.

Create directory Snapshot in Tests/Input/Region_4/2006_01_01.

vgos, lon to longitude, lat to latitude.

Add a test for successive_overlap with periodic grid.

Add snapshot for region 4 at a different date, in input files, for a
new test of successive_overlap.

targetted a single main program.

In script plot_snapshot.py, with option --light, do not plot invalid
outermost contours.

procedure so it can be used by program test_set_all_outerm.

Move dummy argument corner of set_all_outerm to last position.

Bug fix in procedure get_snapshot: urc(2) must always be lower than
nlat, even if periodic is true. Fix the same bug in procedure
set_all_outerm: llc(2) >= 1 and urc(2) <= nlat even if periodic is true.

Bug fix in procedure set_all_outerm: the lower bound of dummy argument
ssh is not always 1.

Make script examine_ssh_values.py work for a periodic domain.

Make program test_set_all_outerm work for a periodic
domain. max_radius is now chosen at run-time (we must change it for
a very coarse grid). Add a corresponding test.

In written shapefiles, replace field "area" by field "r_eq_area",
that is radius of disk of equal area. This is a smaller number so it
needs fewer characters, especially for a global coarse grid.