Revamp the sparse cost matrix.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
SparseCostMatrix: must now specify the number of columns at construction.

In the event of having the last columns empty, even if we forbid it.

Also: to solve LAP we impose that all columns have at least one cost.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Revamp JVSUtils.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
JonkerVolgenantSparseAlgorithm: fix a bug in the column reduction step.

We cannot user standard array iterating initializer for a sparse matrix.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
WIP: tests and benchmarks and debuggin facilities for JVS.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>