Change the schema of json files of -info-json-dir

[yutaro-sakamoto]

This pull request changes the schema of json files generated by a new option -info-json-dir. (See #362)
The following is an example.

callee.cbl

       IDENTIFICATION   DIVISION.
       PROGRAM-ID.      callee.
       DATA             DIVISION.
       WORKING-STORAGE  SECTION.
       LINKAGE          SECTION.
       01 P1            PIC X ANY LENGTH.
       01 P2            PIC 99.
       PROCEDURE        DIVISION USING P1 P2.
           GOBACK.

the JSON file

{
  "opensourcecobol4j_version": "1.0.20",
  "program_id": "callee",
  "procedure_division_using_parameters": [
    {
      "variable_name": "P1",
      "java_type": "String"
    },
    {
      "variable_name": "P2",
      "type": "int"
    }
  ]
}