Remove component radius4 of derived type eddy and field radius4 of
`outermost_contour.dbf`. They are not used any longer.

Because `test_set_all_outerm` is now essentially the same as
`inst_eddies`. Replace `test_set_all_outerm` by `inst_eddies` in
tests.

Move the second test on `self._ishape_last[i_slice][orientation]`
inside the first test. Avoid the double test on
`self._ishape_last[i_slice][orientation]` when
`self._ishape_last[i_slice][orientation]` is not None on entry of the
function. If `self._ishape_last[i_slice][orientation]` is not None on
entry of the function then, necessarily, the assertion on
`self._ishape_last[i_slice][orientation].size` and the definition of
`self._e_max[i_slice][orientation]` have already been done because
`self._ishape_last[i_slice][orientation]` and
`self._e_max[i_slice][orientation]` are only defined from the function
get_ishape_last.

In function `comp_ishape`, return None instead of crashing if eddy
index is greater than max. This allows the script
`write_date_range.py` to work with an input SHPC containing a date
without eddies.

In function `comp_ishape`, check that `eddy_index` is in the right
range.

Preparation for a check in `comp_ishape`.

Dictionary instead of list, following update of `test_compare.py`.

On second thought, I find the default value confusing. We are
reverting commit b328ab6f.

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.