Do not include `write_eddy.f90` in source files of `eddy_graph`. It is
no longer needed since commit 50d2f596.

Assume that a slice is in a directory
"{shpc_dir}/{orientation}/Slice_{slice}" where shpc_dir can be any
name, orientation is "Anticyclones" or "Cyclones" and slice is an
integer. Do not read or create any longer a file "orientation.txt" in
the slice directory. Add procedure `get_slice_dir`. Add dummy
arguments cyclone and slice to procedure `shpc_open`. Add dummy
argument slice to procedure `shpc_create`.

The bug existed since commit 627df958.

Define two variables `hshp_in` and `hshp_out` to avoid aliases in
arguments of `shpc_create`. I have encountered a run which crashed there.

Not needed since commit 53e5c983.

Not needed since commit 6dc504df.

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

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

Rename procedure `write_snapshot` to `save_snapshot`.

Move `Common/write_snapshot.f90` to `Overlap/Tests/save_snapshot.f90`.

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.

Because we are going to use it in `Inst_eddies` too.

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.