Business Layer; ISKeyValueList.GetDouble now supports an option to return Nan as zero

The ISKeyValueList Business Layer object's "GetDouble" function now supports an option to return Nan (Not a Number) as zero.

The function's signature is now GetDouble(key As String, Optional defaultValue As Double = 0, Optional returnNanAsZero As Boolean = False).

This makes it easier to handle Double type variables where "Nan" is a possible value stored in a key/ value pair.