If there are two speed-contours and they do not intersect, check
whether outermost contours intersect. The intersection threshold for
outermost contour is defined by new variable `min_inters_out`. Note
that the default value is such that results are not changed by this
commit if `min_inters_out` is left to its default value.

Distinguish the 4 cases with or without speed-contours. Preparing for
the new structure. We still have not changed any result.

Preparing for the new structure. Note that the code is
degraded (temporarily) because the definition of `polyline_1` is
repeated uselessly inside the loop on `l`.

Optimize: immediately return false if `min_inters` > 1.

Preparing for more complex association criterium.

Preparing for more complex association criterium.

Preparing for more complex association criterium.

Optimization.

Because we are going to complicate the criterium of association
between two eddies.

Because we are going to introduce another variable for the
intersection of outermost contours.

This is not really useful. If necessary, we can extract a component
with `extract_component_nx.py` or `extract_component.py`.

The description was wrong since commit e35226da.

Do not use option `--node` in test of `plot_components.py`, since we
are going to remove it.

Move function `partition_graph_date` from script `report_graph.py` to
script `edgelist_to_Graphviz.py`. `partition_graph_date` is no longer
used in `report_graph.py`.

Because we are going to add a function and we will need to import
`edgelist_to_Graphviz`.

The Graphviz file can be created with `edgelist_to_Graphviz.py`.

`argparse` is overkill here.

Just write a new edgelist. The Graphviz file can be created afterwards
with `edgelist_to_Graphviz.py`.

Move part of tests to new test series in sub-directory.

Rather than from current series of tests.

Move Python scripts to new sub-directory `Analysis`.

Move component extraction functionality to new script
`extract_component_nx.py`. For clarity.