Improve direct dilution, add intermediate dilution when cannot do without

Direct dilution can sometime propose solution that produce more than the expected volume of output plasmid, and thus as for a negative volume of water. On the other side the 10x dilution will always propose a solution.

An optimal intermediate dilution could be computed where intermediate dilution are only proposed when they are the solution in order to not produce more than the expected volume of output plasmid. The constraint to minimize would be the number of intermediate dilution needed.

This could be implemented with mixed integer linear programming (with pulp).