Fix: trackable data types stored into DataNode.value causing encoding errors

[Domiii]

Notes:

• Problem: shelljs has a ShellString object data type that sets its prototype to String, causing valueCollection to miscategorize it.
• ShellString is defined here.
• The encoder uses Object.keys to iterate over props
• The encoder has the following logic for objects:

        if (typeof object === "string") {
            this.encodeString(object);
        }
        else {
            this.encodeObject(object, depth);
        }

• because that is different from how we detect things, ShellStrings get classified as "non-trackable" and thus their value is stored as-is into DataNode, via valueCollection.registerValueMaybe.

TODO

• fix our object detection mechanism, or simply add an extra serialization step before storing plain values on DataNode
• test w/ require4.js