When creating a parametrised query the leading $ is discarded

[Wojtek Czekalski]

When I create a parametrised query like this:

   query ($contentType: String!) {
     File(contentType: $contentType) {
       id
     }
   }

The result is:

"query (contentType: String!)  {\\nFile(contentType: $contentType)  {\\nid  \\n}\\n}"

It is invalid, because the desired result is:

"query ($contentType: String!)  {\\nFile(contentType: $contentType)  {\\nid  \\n}\\n}"

[Ulrik Strid]

#4 should solve this issue. Also adds the ID scalar and treats it as a string.