Multi-Dimensional Array Handler: Access multi-dimensional arrays with a single key

This class can be used to access multi-dimensional array entries with a single string entry key.

It allows to reference elements of an array an arbitrary depth using a single string that represents the element array indexes separated with commas.

The class can take an element index string and set or get its value, check if the element is set, or check it is empty or return the count of entries if the element is an array.