Aded Data Helper and Session Helper

These are two objects I find myself using a lot. I feel like the Class Name "Data" might be a bit too generic and would advise an alternate name, nothing came to mind right away.
Based on many conversations I've had about this subject, the answer is almost always "if the value exists, that's the value I want". Returning the default value instead of a **defined, but `null` value** causes edge cases that are overly difficult to address in specific situations. To that end, going with `array_key_exists` should, ultimately, result in fewer bug reports about this behavior.