The attribute written was always true.

Allow missing `ishape_last.txt` in method `comp_ishape`. This is
useful is an SHPC is missing an orientation.

Use out_cont%closed instead.

Add default initialization for component area of derived type
`ssh_contour`, because we are going to keep contours for which we will
not compute area.

Use test `Region_5_15_days` instead of outside experiment `Inst_eddies_4`.

Add default initialization of component `coord_proj` of type
extremum. As the type of `coord_proj` is integer, there may not be a
compiler option to initialize it. We want to detect when it has not
been defined.

We will need this new shapefile in program `eddy_graph` only for a non
longitude-latitude grid. We add a new dummy argument `grid_lon_lat` to
procedure `shpc_create` to decide whether we create the shapefile
`extr_proj`.

Because we are going to use it also for another shapefile than extremum.

Use component with type extremum in derived type eddy, instead of
components `coord_extr` and `ssh_extr`. Component `coord_proj` of
derived type extremum also replaces component `ind_extr` of derived
type snapshot.

Add component `innermost_level` to derived type eddy. So
`innermost_level` does not transit as an argument through main program
unit `inst_eddies` any longer.

Rename file `test_write_eddy.f90` to `test_write_null.f90`. The name
was badly chosen because the program is not a unit test of procedure
`write_eddy`. In fact, it does not even call `write_eddy`.

Update `CMakeLists.txt` files to take into account commit 3289c070.

Remove unused procedure weight and corresponding unit test. weight is
not used since commit edb16459, after tag v0.20.

We are trying to define clearly the directories and what Fortran files
they should contain:

- `Inst_eddies`: May only contain program units which make up the
program `inst_eddies`. If a program unit does not go into
`inst_eddies`, it should not be here. Not all program units going into
`inst_eddies` must be here: some could be in directory Common.

- `Inst_eddies/Tests`: Main programs of unit tests for procedures in
directory `Inst_eddies`. Plus procedures used only in these unit tests.

- `Overlap`: May only contain program units which make up the program
`eddy_graph`. If a program unit does not go into `eddy_graph`, it
should not be here. Not all program units going into `eddy_graph` must
be here: some could be in directory Common.

- `Overlap/Tests`: Main programs of unit tests for procedures in
directory `Overlap`. Plus procedures used only in these unit tests.

- Common: Procedures that are used in both programs `inst_eddies` and
`eddy_graph`.

- Common/Tests: Main programs of unit tests for procedures in
directory `Common`. Plus procedures used only in these unit
tests. Plus procedures used in unit tests of both `Inst_eddies` and
`Overlap` directories but not used in either program `inst_eddies` nor
`eddy_graph`.

Remove dummy arguments nlon, nlat, corner, step of procedure
`read_snapshot`, use module variables instead. Note that we keep copy
as a dummy argument instead of using the variable of module
`config_graph_m`, because we want the procedure `read_snapshot` to be
usable outside of the `eddy_graph` program.

Add `config_graph.f90`and `read_grid.F90` to lists of source files.

Which read namelists. Motivations: diminish the number of arguments of
procedure overlap; lighten the main program unit. We conditionally
compile MPI calls in `read_grid` because we want to use variables of
module`read_grid_m` in procedure `read_snapshot`, and `read_snapshot`
is called from sequential program `test_nearby_extr`.

Superceded by class `SHPC_class`.

The immediate motivation comes from tests `Mat_v6_to_shapefiles` and
`Plot_eddy_contours_Mat`. `Plot_eddy_contours_Mat` needs to open the
SHPC in `Mat_v6_to_shapefiles`. `Mat_v6_to_shapefiles` does not create
`n_slices.txt` and we do not want to create `n_slices.txt` in
`inst_eddies_v6.py` because this script could be run in parallel for
several slices. There is no simple way to create `n_slices.txt`
automatically after runnning `inst_eddies_v6.py` in the test
`Mat_v6_to_shapefiles`. We cannot use a redirection in a command of
the test so something like `echo 0 > n_slices.txt` would not work.

Note that orientation = None is passed to `get_ishape_last` where it
becomes `self.def_orient`.

Move function `comp_ishape` to method of SHPC class.

Several scripts allow `ishape_last.txt` not to exist. For example
`eddy_dump.py`.

The code is adapted from `filter.py`.

Especially, we want to allow missing layer `max_speed_contour` when
running script `plot_eddy_contours.py`.

The motivation is to manage an SHPC directory without opening first
all the files inside. The class allows to open files dynamically and
remember already opened files.