Raise MemoryError proactively in certain cases #2

In NMSIM_InputOutputTools.tbx, it seems appropriate to anticipate that some users may try to create projects so large that NMSIM will crash. This should be handled in advance.

There are two prerequisites:

1. What is NMSIM's memory limit? (Presumably constant.) Convert to a maximum area.
2. How to extract the area of the Study Area Polygon from the Attribute Table using SearchCursor? Should be pretty easy.