`slice` is a built-in class of Python.

A little clearer, a little less repeated code.

If `date < handler["d_init"]` then the result of the function is
silently wrong.

The global variable was used in the body of the function.

Adapt to the new definition of an SHPC.

Adapt to the new definition of an SHPC.

Rename `get_SHPC` to `get_slice` and `i_SHPC` to `i_slice`.

Move files from `Anticyclones/Slice_0` to `Slice_0/Anticyclones`.

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.