Following updates of the libraries.

Following updates of the libraries.

Move the call to `find_package` for EZMPI to
`Overlap/CMakeLists.txt`. We are reverting in part commit f04aea8b
since `test_set_max_speed` no longer uses MPI.

Note that programs `test_max_speed_contour_ssh` and `test_weight`
depend on fortranGIS through the module derived_types. Compilation
worked without linking to fortranGIS because objects used by
`test_max_speed_contour_ssh` and `test_weight` in
derived types do not use fortranGIS.

Because we are going to add preprocessor directives.

Remove `shpc_create.f90` from source files of target `eddy_graph`. It
is no longer needed since commit 50d2f596.

In case we are a sub-project.

In procedure overlap, write an edge across delta days instead of delta
edges across single days. So we do not need procedure `write_overlap`
any longer, nor program `test_write_overlap`.

Rename triplet to collection, `shp_tr` to shpc, shpt to shpc in
comments, identifiers and file names.

We are reverting commits 35fad1b7 and df2b397d because we want the
program `eddy_graph.sh` to read an SHPC containing a single
orientation.

Because we are going to use it in `test_nearby_extr`.

Use higher level procedures in main program
`test_set_max_speed`. Allows to read easily more information: cyclone,
`ssh_extremum`, `coord_extr` from the shapefiles. So we do not ask
this information to the user. The drawback is that we have to call
MPI (because of `read_field_indices`) even if we do not really use
it. We move the calls to `find_package` for EZMPI and `GPC_F` to the
top-level `CMakeLists.txt` since these libraries are now necessary in
both `Inst_eddies` and Overlap.

`read_eddy.f90`, `read_field_indices.f90` and `shp_tr_open.f90` will
become common to Overlap and `Inst_eddies` because they will be used
in `Inst_eddies/Tests/test_set_max_speed.f90`. So there are now enough
common files to justify a new directory.

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

Also split the tests, Fortran source files, Python files and JSon
files. Keep at the top level the files used in both `Inst_eddies` and
Overlap.

Motivations for the split:

- The top directory contained many files.

- It may be useful to compile only one of the two sub-projects. For
example, only `Inst_eddies` on Ciclad, where MPI 3 is not available.