This required changing the constant values (e.g. kSize) into functions
(e.g. GetSize()).
Fixed implementations of ForEachNested to be inline (as these are actually
templates).
Also added a ntcore Struct test.
This implements de/serialization for the types that aren't templated (SwerveDriveKinematics) in C++ or where there is no trivial way to go round-trip (Splines) for the messages.