Change way we expose .NET objects (e.g., sqlite)

[isaksky]

We should do it like it is done in ClearScript:

https://github.com/microsoft/ClearScript/blob/1d2800b2575863b4de9cc2cb6d05c4b2623b49f4/ClearScript/V8/V8ScriptEngine.InitScript.js#L4

1. Deref .NET props
2. Delete .NET props
3. Freeze
4. Expose