Convert a native object to an instance of QueryField

[kbarbounakis]

Description
The latest version of @themost/query supports the conversion of a javascript object to an instance of QueryField class e.g.

{
    "productName": "$product.name"
}

or

{
    "producDescription": {
          "$concat": [
                 "$product.model",
                 " ",
                 "$product.name"
         ]
     }
}

This feature should be supported also by the LTS version.