[FaceRest] Add implementation of handlerGetAccessInfo().

But it's not tested yet.
The json format may be changed later.

An example of current format:
{
  "apiVersion": 3,
  "errorCode": 0,
  "numberOfAllowedServers": 2,
  "allowedServers": [
    {
      "id": 1,
      "numberOfAllowedHostGroups": 2,
      "allowedHostGroups": [
        {
          "id": 1,
          "accessInfoId": 1
        },
        {
          "id": 2,
          "accessInfoId": 2
        }
      ]
    },
    {
      "id": 2,
      "numberOfAllowedHostGroups": 1,
      "allowedHostGroups": [
        "id": 1,
        "accessInfoId": 3
      ]
    }
  ]
}