Use JSON.parse/stringify to clone an object

[p3k]

We noticed that the clone() function can cause an error if the constructor property is not a function.

This is a (rare?) case when a POJO has a property named constructor:

{
   "building": "House A",
   "constructor": "Construction Company Ltd."
}

This PR replaces the main part of the clone() function with the JSON.parse/stringify combo.