Remove value types: Struct -> Class

[Mooshua]

Unless there's a very good reason why we should have these as value types, these should be reference types.

Reference types have more features and makes it easier to use dynamic .NET (eg reflection) in the API.

[fuzzbuck]

+1
If a struct allocates more than 16 bytes, or is used in an async closure it is allocated on the heap anyway.
There is no benefit to using structs over classes here, and classes give more versatility.

[MapleEve]

This will be a huge huge redo if the communication struct is changed, so i doubt unless the gameserver itself has done the part and Oki is free, currently the part is most likely the same as it is in gameserver.