Array Generator: Initialize arrays using several methods

This is an extension of the Array class that can initialize arrays using several methods.

It provides several new functions for the Array that can setup the elements of the arrays with specific values. Currently it can:

- Populate the array with a given number of keys
- Set the array elements with a range of values between two numbers
- Set the array elements with an incremented or decremented range of numbers starting from the element 0 to a given number
- Set the array elements with a given range between two numbers but having a given gap between each element
- Set the array elements with a range of letters of a given length starting with A
- Repeat the value of the element 0 a given number of times
- Set the array elements with values of a given formula callback