Large initLookups function crashes on entry

[ToddFincannon]

When a model has a large number of lookups or data variables, the initLookups function can become too large and crashes on entry.

[ToddFincannon]

We can use chunkedFunction the same as with initConstants to break up initLookups into smaller functions. The only wrinkle is that initLookups generates C lookups for both Vensim lookups and data variables, which are implemented with lookups. To use chunkedFunction, we need to add a separate initData function that handles data variables.