add to create_region_input.py to create soil texture input file.
add to create_region_input.py to create soil texture input file.

Trying to mimic Helene's DOS-TEM setup by providing/using explicit
percentages for sand,silt and clay, instead of using texture classes.

tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem