All derivative terms added
Feature: forwardSimulate now returns a new state

forwardSimulate was modifying always the same state modifying it
by side effects.

Next: Find the reason that raises an exception in the solver
 Forgot the diagonal terms. Some derivatives are still wrong
FIX: Simulation jUnit test
FIX: Initial densities derivative terms were -1 instead of 1
Correction of mass conservation deerivative terms
Small refactoring
Simplifying the computation of dJ/dU
BUGFIX: The vehicles at the destinations were included in the cost function
BUGFIX: The supply of a sink is density/delta_t instead of just density
Feature: Now we also compute the evolution at time T-1 and drp the one at T

We want to have the correct values for the demand/supply/in and out-flows
even for the last state for time step T-1
A state including also the sum of the split ratio, run() must not be visible
Update of the jUnit tests after the previous modifications
Initiation of a test checking for derivatives terms
The next field in the cells was not properly initialized

This field is never used to there is had no influance. But for probable
future search in the graph, it will be needed.
Small refactoring
New feature: we can now decide the share of the compliant commodities

The non-compliant commodity has been removed from the control vector since
it is not a variable
Modification: Automatic initialization of the initial variables for the solver

The barrier concerning the sum of the split-ratios was at 0.999. Now this
barrier is at 1 and the initial split-ratios is a not physical set.
BUGFIX: When the demand is zero, we do not put any barrier in J
Small corrections