Symbolic links in the Aviso `All_SymbolicLinks` directory point to
absolute paths so they do not work (I think) if we choose to mount the
Aviso directory through sshfs.

Read date from `date_range.txt` in program `inst_eddies` and update
date in `date_range.txt`at the end of execution of program
`inst_eddies`, remove date from the namelist `main_nml`.

Rename type `shpc_slice_handler` to `ori_slice_handler`.

Use `create_slice.py` in tests of program `inst_eddies`. The namelists
then have to be written to a file, to be read both by
`create_slice.py` and by the program `inst_eddies`.

The program `test_mean_speed` no longer needs the SHPC directory since
commit 8eadc458.

Only write `used_config_nml.txt` and `grid_nml.txt` if `leave_trace`.

Promote u and v to variables of module `input_ssh_m`, and remove them
as dummy arguments of `input_ssh`, `set_contours`, `mean_speed` and
`set_max_speed`. u and v are defined in procedure `input_ssh` and used
only in procedure `mean_speed`.

Remove dummy argument corner of function `mean_speed`, not used any
longer.

The case of u and v is different from the case of ssh. For ssh, we
want to restrict as much as possible the size of the array we work
with because we search all the contours in the corresponding
window. But for u and v, we only do a bilinear interpolation, without
a call to locate or hunt within the interpolation procedure, so there
is nothing to be gained to work on only a window of u and
v. Furthermore, we are preparing to allow staggering of the u and v
grid with respect to the ssh grid so if we wanted a window of u and v,
there would be the complication of choosing the window taking the
staggering into account.

It was not convenient to read them with input function or on the
command line: too much to read this way, and not clear when saved in
JSON text file. And we already had to create a namelist file
anyway. And this way the namelists can be extended transparently.

Instead of `config_nml.txt`. Preparing to include other namelists in
this file.

Bug fix: do not provide standard input for `inst_eddies_Aviso.py`, it
does not read it.

In the case of non-uniform longitude-latitude grid: we read the whole
coordinate arrays from the NetCDF file; we have a different way of
inverting the projection, in `invert_proj`; the program `eddy_graph`
does not use `corner_whole` and step, which are not defined, it uses
instead the shapefile `extr_proj`.

Preparing to generalize to a non-uniform longitude-latitude grid.

In program `test_mean_speed`. To make it work with a non-uniform grid,
we would have to read a contour in projection coordinates.

Use `uniform_lon_lat` from modules `input_ssh_m` or `read_grid_m` to
compute actual argument of `shpc_create`.

In program `examine_eddy`.

Replace dummy argument `grid_lon_lat` of procedure `shpc_create` by
`with_proj`.

Specify whether to read shapefile `extr_proj` in procedure `shpc_open`
instead of just trying to read this shapefile. Use `uniform_lon_lat`
to decide whether to read the shapefile. As `shpc_open` is called in
both programs `inst_eddies` and `eddy_graph`, we cannot access
variable `uniform_lon_lat` of module `input_ssh_m`, which is not used
in program `eddy_graph`, nor variable `uniform_lon_lat` of module
`read_grid_m`, which is not used in program `inst_eddies`. So we add a
dummy argument `with_proj` to procedure `shpc_open`.

Rename variable `corner` of module `input_ssh_m` to `corner_whole`.