Bug fixes and new data files

ecospat function on line 93 for irrigated potato now references the
stacks of climate data correctly.

Bugfix on line 104, removed extra ")"

Addition of Cache/Planting Seasons/CRU_CL20_Potato_Plant.grd/.gri files
for rainfed, irrigated and combination rainfed and irrigated planting
seasons and predicted by EcoCrop. These files can be used with the
SimCastMeta model for predicting the planting season of potato.