Rename `main_nml` to `config_nml` in module `config_m`.

Extract code from program `inst_eddies` into new procedure `write_snapshot`.

Extract code from program `inst_eddies` into new procedure `input_ssh`.

Split derived type `shpc_slice_handler` into `shpc_slice_handler` and
`shpc_slice_meta out`. Do not mix what is necessary to open, create
and close, analogous to a logical unit, with what comes from reading
the files.

Create component `unit` for `ishape_last.txt` in derived type
`shpc_slice_handler`. Open, create and close `ishape_last.txt` at the
same time we open, create and close the shapefiles. So we use
`read_opcol` instead of `read_column` when we need to read
`ishape_last.txt`.

We are more clearly separating opening files and reading from them.

This is no longer needed since commit d16d3f1c.

Use `e_overestim.txt` instead of `node_id_param.json`. Since commit
43d2eff6, we wrote only `e_overestim` to the JSon file. Simpler to
write the value alone in a text file.

Add tests for a case where the speed is not defined on a whole segment.

Move tests `Plot_eddy_contours_Mat` and `Stats_Matlab` to
`Convert_Matlab/Tests/long_tests.json`. Thus, we group the tests that
depend on the availability of Matlab.

The modification of `sys.path` was added in commit 034d96fe to have
access to `util_eddies`. It is no longer useful, since commit
d16d3f1c, when a symbolic link was added.

To ease comparaison of runs. Also to unclutter standard output when we
run thousands of dates.

Because it contains timing.

Following update of `test_compare.py`.

In pandas for example, a column header name containing a blank is not
convenient.

We can make a symbolic link or copy to `$large_input_dir`.