Merge branch 'bishtgautam/lnd/add-soilp-to-fsurdat' (PR #1603)

Adds soil phosphorus to land surface dataset

Updates the land surface dataset generations scripts to include
following soil phosphorus data in surface dataset:
1 APATITE_P
2 LABILE_P
3 OCCLUDED_P
4 SECONDARY_P

Adds mapping files for soil phosphorus dataset at following
resolutions:
1 0.9x1.25
2 1.9x2.5
3 ne30np4

[BFB]