Add wood harvest/products parameters to CABLE namelist file.

[tammasloughran]

The wood harvest/products parameters are hard coded into the CABLE-ACCESS interface. There is no technical reason to have these parameters hard coded and they are important for tuning the land use change/thinning components to get reasonable land-use emissions. I will move them into the CABLE namelist file.

These parameters are:

REAL :: pool_frac(3) = (/0.33,0.33,0.34/) !! Fraction of harvested biomass allocated to the wood products pools
REAL :: pool_time(3) = (/1.00,0.10,0.01/) !! Timescale of wood product pool decay to the atmosphere (year^-1)