Interception

[mdekauwe]

The interception code I've added borrows from CABLE and is consistent with the simple nature of the day model.

• One could look at replacing this with the Rutter model
• The current scheme ignores any drainage from the canopy store during each time step. There is "spill" but no drainage.
• Need to consider whether we go down the route of using some of the wet fraction of the canopy to meet atmos. demand. Currently we are not as before.

[mdekauwe]

The integration routine is now in the code as part of the hydraulics, so one could add the Rutter scheme if desired.