Move serialization/deserialization code into common library

[stcheng]

these piece of code will need to be as part of the shim layer wrapping the database, so that every type of data can be stored in the database in the same format.

[kcudnik]

Yes, i think the same will apply to the sai validation logic, there are some tricks that needs to be done on the go (about those lets talk offline). As for serialization, after having metadata we can change entirely serialization logic to produce more user friendly names, still for this metadata is needed.