Changing my mind. In an SHPC, store shapefiles in
"Slice_{slice}/{orientation}" instead of
"{orientation}/Slice_{slice}". Two reasons: easier to store accessory
files from running `inst_eddies`, such as `perf_report` and output
from Torque submission script; clearer that a slice should contain the
same dates for both orientations.

Call `write_snapshot` from `save_snapshot` instead of `write_eddy` directly.

Read `used_nml.txt` at the SHPC level, only one file for both
orientations. Remove dummy argument exist of procedure config. Demote
`config_nml` to local scope. Remove procedure `write_nml`.

Remove procedure `write_aux`. Write to `ishape_last.txt` in procedure
`write_snapshot` and write `grid_nml` in procedure `input_ssh`. In
`input_ssh`, if `grid_nml.txt` already exists, check consistency with
input NetCDF files. Downgrade dummy arguments `corner_deg` and
`step_deg` of `input_ssh` to local variables. Read and write
`grid_nml` at SHPC level, only one file for both orientations and all
slices.

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`.