Add JSON field transformation

[Mikescops]

This PR allows to use JSONPath transformation on fields.

Given this JSON file:

You can do such operations:

{
"store": {
  "book": [
    {
      "category": "reference",
      "author": "Nigel Rees",
      "title": "Sayings of the Century",
      "price": 8.95
    },
    {
      "category": "fiction",
      "author": "Evelyn Waugh",
      "title": "Sword of Honour",
      "price": 12.99
    },
    {
      "category": "fiction",
      "author": "Herman Melville",
      "title": "Moby Dick",
      "isbn": "0-553-21311-3",
      "price": 8.99
    },
    {
      "category": "fiction",
      "author": "J. R. R. Tolkien",
      "title": "The Lord of the Rings",
      "isbn": "0-395-19395-8",
      "price": 22.99
    }
  ],
  "bicycle": {
    "color": "red",
    "price": 19.95
  }
}
}

dcli read 'dl://books.json/content?json=$..*[?(@property === "price" && @ !== 8.95)]'
[19.95,12.99,8.99,22.99]

JSONPath system (quite similar to jq) is explained here: https://github.com/JSONPath-Plus/JSONPath#syntax-through-examples