Changeset 1252

Finalized separation of option Cforcing_file and spinup_analytic, they can now be used independently :

• variable nbyear is now only used for Cforcing_file

• added new parameter spinup_period. This should be set to the number of years of forcing data used in the spinup analytic. For stability resons, if spinup_period is less than 7, then it will be adjusted to 10 years (same functionllity as before).