Require options.JULY_TAVG_SUPPLIED when options.COMPUTE_TREELINE == TRUE
Consistent use of ErrStr (+1 squashed commit)
Squashed commits:
[a452dbe] Reformat and consistent use of ErrStr
Removed duplicate #include <stdarg.h>
Compute snow bands that are above the tree line
Additional vegetation checks
Calculate vegetation parameters during initialization

Needs testing to ensure that the number of vegetation types and bare soil are managed correctly under all circumstances. Particularly when the above treeline option is active.
Added MONTHSPERYEAR to replace hardcoded 12
Added utility print functions for veg_con_struct and veg_lib_struct