serialization, de-serialization of script definitions

[damooo]

We should provide functionality to serialize & de-serialize ScriptDefinition and ScriptScheme types.

This way we can transfer definitions from server on demand, and dynamically instantiate ScriptDefinitions. This is useful, when we don't want to package all scripts in code, but seek them on demand.

This is low priority though. As presently packaging all scripts is not that heavy weight thing.