Compute `i_slice` in `comp_ishape` if `i_slice` is None. Add default
value of None for dummy argument `i_slice`.

Move dummy argument `i_slice` of function `comp_ishape` to last
position. Because we are going to add a default value.

Except with option `-i`, which still assumes slice 0.

Move functions `node_to_date_eddy` and `date_eddy_to_node` from script
`report_graph.py` to script `util_eddies.py`. `util_eddies.py`
contains more basic functions, it only imports
shapefile. `report_graph.py` imports networkx. It was not convenient
nor meaningful to require networkx for scripts that use
`node_to_date_eddy` or `date_eddy_to_node`.

Invert order of dummy arguments orientation and layer of method
`get_reader`. Take the same order than in the path. `orientation` was at
the end because, at first, in commit d858fb72, it was an optional
argument.

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

Move function `comp_ishape` to method of SHPC class.

Avoid the mistake eddy_index = 0.

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`.

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.

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.

Instead of several values of the handler dictionary. Clearer and more concise.

Instead of tuple. Preparing for extensions to return orientation and
to deal with several SHPC.

Using `ishape_last`, instead of iterating through the shapefile.

From directory Analysis. Extract corresponding tests from
`Analysis/tests.json` into new file `Inst_eddies/Analysis/tests.json`.

In script `eddy_dump.py`, do not assume that there is a single date
index. So find ishape by iterating through values of date index and
eddy index.

Add a test of overlap in `short_tests.json`.

Take into account new policy in `filter.py`: the names of the three
shapefiles are always the same and form a unit in a snaphot directory.

Rename `compil_prod_dir`to `build_dir` in JSON test files. Add a test
of `successive_overlap` with global grid, normal resolution.

Take into account new policy in `filter.py`: the names of the three
shapefiles are always the same and form a unit in a snaphot directory.

Rename `compil_prod_dir`to `build_dir` in JSON test files. Add a test
of `successive_overlap` with global grid, normal resolution.