We rewrite `inst_eddies_Aviso.py` so it is more convenient to use. The
script is only useful for several input files. Otherwise we can
directly use `inst_eddies.py`. So instead of optional arguments
template and last date, we use positional arguments. Then there is no
point in distinguishing dirname and basename. Also, it does not make
sense any longer to read the date from the content of the first
file. The script becomes more general: we do not assume that all input
NetCDF files are in the same -directory and that the time coordinate
is in days since 1950-1-1. The interface is also clearer.

We need ssh of extremum in `set_contours`, to compute `innermost_level_2`.

Because we are going to use it for another field.

Instead of standard output.

Since it is not in the shapefiles.

Remove option `--dashed` of script `plot_eddy_contours.py`. This
option was added in commit 5e0e0deb. The dummy argument dashed of
function snapshot is useful because we can call snapshot several times
on the same axes from elsewhere, but I do not see how the option
`--dashed` of script `plot_eddy_contours.py` is useful, since we
create a new figure when we run the script.

Check that `SHPC_dir` exists at initialization of instance of class
SHPC. Before this commit, if `SHPC_dir` did not exist, there was an
error trying to create `n_slices.txt`, which was less clear.

Add the possibility to write `cont_list` from `set_contours`. We want
to do that without impacting the main program unit `inst_eddies`. We
do not want to centralize variables at hight level in
`inst_eddies`. So we do not want to promote `cont_list` and `n_cont`
to dummy arguments of `set_contours`.

Split dummy argument `e` of `set_contours` into relevant components.
Motivation: make appear clearly input and output.

Split dummy argument `e` of `set_max_speed` into relevant components.
Motivation: make appear clearly input and output.

Replace dummy arguments `s` and `i` of procedure `set_contours` by
dummy argument `e`.

Move the computation of the search window for the outermost contour
and `outside_points` from procedure `set_contours` to main program
unit. The motivation is to have a clearer interface of procedure
`set_contours`, without `s` and `i`.

Rename module `set_all_contours_m` to `set_contours_m` and procedure
`set_all_contours` `set_contours`.

Rename file `set_all_contours.f90` to `set_contours.f90`.

Move the loop on eddies out of `set_all_contours`, up into the main
program unit. The motivation is to be able to easily study a
particular eddy, having access to `cont_list` and corresponding speed
values.

Bug fix: manage absence of a good contour within the outermost
contour.

Create a new figure in function `plot_distr_funct` if ax is None.