ENH: Adding Python Array Accessors for Derived Value Items

The C++ ValueItemTemplate class provided methods of setting multiple values of the item using iterators. Unfortunately these methods could not be made available in the Python wrapped API. Instead we have added setValues and values methods to the pybind11 wrapping for DoubleItem, IntItem, and DoubleItem which allows the use of Python arrays to set (and get) all of the values of the Item.