shr_string_listCreateField(), but for any range

I need to create a field list for a range of values that does not begin with 1. This doesn't work with `shr_string_listCreateField()`, which uses the input `numFields` as the top of the range and 1 as the bottom. I suggest implementing a new function, `shr_string_listCreateField_range()`, which takes inputs of the bottom and top of the range.

I've already written this up in a fork and will submit a pull request shortly.