Added URL rewrites data to the product interface

[rogyar]

Description

Added URL rewrites data to the GraphQL product interface. So, now we have a possibility to fetch all URL rewrites for a product with request URL data and target URL parameters.

Also, the old UrlRewrite resolver has been renamed to EntityUrl to make the class name match its purpose.

Fixed Issues (if relevant)

1. Return URL Rewrites for products #84

Manual testing scenarios

• Create a product with name "configurable" and assign it to a category
• Use the following request to fetch the product data:

{
    products (search:"conf") {
        items {
            name,
            sku,
            description,
          	url_rewrites {
              url,
              parameters {
                name,
                value
              }
            }
        }
    }
}

• You should see 2 URL rewrites in the response like in the following example:

{
  "data": {
    "products": {
      "items": [
        {
          "name": "Configurable",
          "sku": "Configurable",
          "description": null,
          "url_rewrites": [
            {
              "url": "configurable.html",
              "parameters": [
                {
                  "name": "id",
                  "value": "5"
                }
              ]
            },
            {
              "url": "some-category/configurable.html",
              "parameters": [
                {
                  "name": "id",
                  "value": "5"
                },
                {
                  "name": "category",
                  "value": "3"
                }
              ]
            }
          ]
        }
      ]
    }
  }
}

[vkublytskyi]

As EntityUrl and UrlRewrite are pretty similar it is better to describe their purpose in class comments (now both classes have same description so to understand what is needed source code should be explored)

[naydav]

Looks like we need to move all of this functionality to CatalogUrlRewriteGraphQl

[naydav]

Pls remove using Factory