Assessment Tool $$hashKey

While using the assessment tool, we store Angulars '$$hashKey' as field name in the DB.
Example: 5543829fed966d112c000009

```
"answer" : 
    { "ideal" : [ 
            { "scores" :   {  }, 
            "golden" : true, 
            "source" : "...", 
            "body" : "...", 
            "$$hashKey" : "055" }, 
```
