Create SOILWAT2 input file and make SOILWAT2 output cell-specific in gridded mode.

[chaukap]

With issue #470 wrapped up we are ready to use the flag created in #465 to only output information for a select number of cells. This will be accomplished by creating a new input file called grid_SOIWLAT2OutputCells.csv. The CSV will be a single line of cell numbers separated by commas.

For example, if I were running a 3 x 3 plot and I wanted the SOILWAT2 output for every over cell I would input

0,2,4,6,8

This will keep the file extremely simple and small.