Extract & Rewrite MessageStruct

[sheldonth]

MessageStruct needs to be class that does some memory management and pointer ownership.

Safely delete the new messagestruct class after the javascript method has been kicked off that moves the data

[sheldonth]

MessageStruct sucks because:

• Struct needn't be part of the name of a C struct used in C++
• It should be a class that does some smart allocation and deletion, and probably manages a smart pointer of it's own to the serialized message data