bug report on the implementation fo transpiration/evaporation Granier vs Jarvis

** Problem of Granier vs Jarvis during the wet-period at the Costa-Rica site : Granier has been modified to properly account for the evaporation of intcerpted water. This implies that part of the energy previously used for transpiration is now used for evaporation. During well-watered period (with a lot of rain) this reduces transpiration. This was not implemented on Jarvis beaucause Jarvis does not relies on energy based estimates of transpiration but rather on darcy’s law. At minima, to solve this : we should modify Jarvis a set the leaf water potential and VPD_leaf to 0 when there is some liquid water on the leaves.