models. It's a better semantic and improve performance as well as
readability of the code. All the tests passes (except the remark in the
last commit).

variableautomaton. It improves performance.

Tests of Cosmos doesn't pass on the bounds (with a parameter equal to
zero). It's a problem of design (there are issues for cosmos too).

copyto! is implemented for LHA states.

Automaton G works almost well, a bias in the distance is identified
compared to Cosmos when one of the model parameters is zero.

Implementation of volatile_simulate, which simulates SynchronizedModel
without saving values: it only returns the last LHA state of the
simulation.

Implementation of distributed computations of variable automata with
volatile_simulate.

Tests passed.

Add of several useful functions for access values of model, lha and
trajectory objects.

First implementation of LHA.
Synchronized simulation not yet tested.
Reading of trajectories with LHA seems to work with one test basted on
simulations that checks that the last value is well read.