Support for Observable

[benbucksch]

On the server

If the server is sending an object that implements Observable (or has a subscribe() method), then:

• Send the object as type observable instead of plainObject
• Send the values of all public properties of the object. Also, the values of all public getters.
• (Make a function isPrivateProperty(propertyName: string) which skips all properties starting with _, starting with #, and possibly others later.)
• Let the server subscribe to the object.
• Once the subscriber is called, send the updated property values to the client.

On the client

If the client receives an object of type observable,

• the client creates a stub (e.g. RemoteObservable), similar to the plain object, but also sets all the properties that the server sent.
• The object implements Observable with a subscribe() method and remembers the subscribers.
• If the server sends updated property values, the client updates the local object, and then calls the local subscribers.

Object lifetime

Pay attention for object lifetime.

• We don't want the client to hold on to objects which don't exist on the server anymore. (Hopefully, the collection observers will take care of that.) In other words, we should not have wild pointers.
• We don't want the server or client to keep objects alive which represent base objects that have been destroyed. In other words, we should not leak.