Code clean-up clarifes that there are two types of soil layer
definition: the node-based and the thickness-based.

User-defined option allows user to specify a soil layer profile in the
form of a dzsoi vector (values in meters) in the thickness-based
approach.

Default nlevsoi for NWP configurations had to change from 5 to 4 for
consistency with the new error check described in known bugs below.

Other code clean-up removes a couple of sections of repeating code.