improve flexibility of the vegetation tables

[martynpclark]

The current use of the vegetation tables is ugly. In multi_driver.f90, the monthly vegetation fraction is hard coded as

 define monthly fraction of green vegetation
!                           J        F        M        A        M        J        J        A        S        O        N        D
greenVegFrac_monthly = (/0.01_dp, 0.02_dp, 0.03_dp, 0.07_dp, 0.50_dp, 0.90_dp, 0.95_dp, 0.96_dp, 0.65_dp, 0.24_dp, 0.11_dp, 0.02_dp/)

and then used to create monthly LAI as

! overwrite the tables for LAI and SAI
 if(model_decisions(iLookDECISIONS%LAI_method)%iDecision == specified)then
  SAIM(typeStruct%hru(iHRU)%var(iLookTYPE%vegTypeIndex),:) = mparStruct%hru(iHRU)%var(iLookPARAM%winterSAI)
  LAIM(typeStruct%hru(iHRU)%var(iLookTYPE%vegTypeIndex),:) = mparStruct%hru(iHRU)%var(iLookPARAM%summerLAI)*greenVegFrac_monthly
 endif

Clearly this specification is too restrictive, especially when using summa for simulations in both the northern and southern hemisphere.

Suggest remove the green veg fraction.