Enables two major changes to the parameterization that calculates LAI
burial by snow: a) pulls stocking density and taper parameters that
influence vegetation height from hard-wired values in
biogeochem/VegStructUpdateMod.F90 to allow to be specified on the
surface file (per main/pftvarcon) and b) updates the LAI burial by snow
rate from Wang and Zeng, 2007 (linear burial) to form proposed
by Liston and Hiemstra, 2011 (linear or non-linear) burial. The Liston
and Heimstra (2011) formulation introduces two new parameters:
1) bendresist, which specifies how resistant branches are to bending
under snow loading (1 = no bending, lim->0 branches bend very rapidly)
and 2) vegshape, which specifies how the shape of the vegetation crown
affects how rapidly it is buried by snow (1 = paraboloid; 2 = hemispheroid).
These new parameters can also be specified on surface file.

Temporary change, pending merge of IM4 updates. IM4
removed a lot of the hard-coded tests that looked
for particular pfts by their assigned number. this required
modifying the helper function "woody" to be a non-binary
(i.e., now 0 = herbaceous, 1 = woody tree, 2 = woody shrub),
but this updated function isn't available to IM3 currently.

The taper array was being initialized incorrectly,
leading to developer test failures. This moves
the definition down further to be able to initialize
correctly.

Adds a new exact restart test that uses new parameters
in the param file for snow/vegetation interactions.

fixes an issue where using less than the maximum pfts
set new parameters with non-physical values