fsurdat_modifier option needed that updates landuse.timeseries files for transient simulations

[slevis-lmwg]

In transient simulations, fsurdat modifications will get overwritten over land areas represented in the landuse.timeseries file. For the fsurdat modifications to be preserved in the transient simulation, we need the same modifications in the landuse.timeseries as in the fsurdat file.

[ekluzek]

This is somewhat related to #1673