Support for complex types (Lists, Tuple-likes)

[Wibble199]

Add support for more complex types of data, such as lists of items (and being able to add, remove, etc.).

Perhaps add support for some sort of field groups (such as tuples or custom classes) which would allow for storing of groups of related data. This would be especially useful when paired with lists.

Having a toggle on variables to allow/prevent them from storing null may also be useful. Will require anything not marked as nullable to have a value (even if it is a reference type, unlike C#).

Will need to consider more cases such as how we would access variables/lists inside these 'groups'.