Cleanup Codec/Serializer/Deserializer contracts

Current definition of these interfaces is rather problematic:

• it does not enforce nullness
• there is no definition of what happens on illegal input
• there is no provision for throwing checked exceptions

Updated the definition of Codec, so that it takes an Exception type to be thrown from serialize/deserialize. Also add a specialization for unchecked expecptions and a concrete specialization for IllegalArgumentException – which is effectively what we are doing now.