Simplify Marshal using new Swift features

[olejnjak]

Hi,

I was wondering whether it would be possible to simplify Marshal implementation using new Swift features like conditional protocol conformance. This would also simplify creating 3rd party extensions above Marshal.

This would e.g. allow [ValueType] to conform ValueType so lot of code could be then reused/deleted.

I'm open to implementing it but don't wanna waste time on something that wouldn't have a chance to be merged.

Thanks

[bwhiteley]

I like the idea of reducing duplicated code.