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

`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.

Update required following commit 05dd4fc1.

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.

Rename files and identifiers: change `"shp_triplet"` to `"shp_tr"`.

Use the components for field identifiers of a variable of type
`shp_triplet` instead of storing these field identifiers in variables
of modules `init_shapefiles_m` and `read_field_indices_m`. The dummy
argument hshp of procedure `read_field_indices` becomes
`intent(inout)`.

Create derived type `shp_triplet`. Motivation: we need to manipulate
two triplets of shapefiles in program `eddy_graph`. Use everywhere a
variable of type `shp_triplet` instead of the three variables
`hshp_extremum`, `hshp_outermost`, `hshp_max_speed` when all three of
them appear. Rename character variable `shp_triplet` to
`shp_triplet_dir`.

Prepare for a run of `test_get_snapshot` which receives a
snapshot. Generalize main unit `test_get_snapshot`: it is now
parallelized; it reads a date index from stdin; it sends a snapshot
from process 1 to process 0 if it is run with 2 processes.

The logic of the overlap program will be that all processes access the
triplet of input shapefiles. So modify subroutine
`read_field_indices`: process 0 reads field indices and broadcasts
them. This implies that programs `test_overlap`, `test_read_snapshot`
and `test_read_eddy` use MPI.

Generalize `algorithm.py`.

In program `test_send_recv`, read input SHP triplet from command line
instead of requiring it to be present in the current directory with
the name `SHP_triplet_old`. Generalize `test_send_recv`: read
`ishape_last` from file. In `test_send_recv`, all processes must now
access the triplet of shapefiles since process 0 reads field
indices. For the sake of uniformity, read and broadcast k1 from
process 0.

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.

validity of an eddy depending not only on its amplitude but also its
surface. (Note that, in this version, the component valid is redundant: one
can simply test the component out_cont%n_points.)

hard-coding them.

Remove component twice of type eddy, no longer needed.