Support for saving and loading as abstracted collection interfaces

[JimmyCushnie]

I.e. you should be able to save and load IEnumerable, ICollection, IReadOnlyList. Internally the library would just handle it like an array

[JimmyCushnie]

Today I refactored the handling of collection types, which will make this much easier to implement. However I've decided to hold off on this feature for now because I want to work on other (non-SUCC) things.

When I get around to this, the full set of interfaces I'd like to support is as follows: IEnumerable<T>, ICollection<T>, IReadOnlyCollection<T>, IList<T>, IReadOnlyList<T>, IDictionary<T>, IReadOnlyDictionary<T>