This can be used by script code for reliably storing Lua values without
having to build a custom serialization format.
The C++ code can also be used by other code modules that want to
serialize data. The new classes simply return a byte array with an
unspecified format.
At the moment this uses a plain JSON encoding but could be extended in
the future to include either compression or BSON encoding if necessary.
The format is future compatible by using a simple header to identify
different kinds of formats.
