Add JSON validation for SearchQueryParameterBean

[Mortinke]

to avoid Exceptions like org.springframework.dao.InvalidDataAccessApiUsageException: max-results cannot be negative, we can add a validation for limit and offset

[Mortinke]

With #31 we have now the following behavior:

• we can find the minimum value for offset and limit in the schema (with rest-schemagen)

          {
              "href": "<api-path>/<listing-path>?offset=0&limit=20",
              "schema": {
                  "type": "object",
                  "properties": {
                      "limit": {
                          "type": "integer",
                          "minimum": 0
                      },
                      "offset": {
                          "type": "integer",
                          "minimum": 0
                      }
                  }
              },

• a RFC-7807 compliant Exception is created if offset or limit is negative

  {
  "type": "https://developers.unite.eu/errors/invalid-query-param",
  "status": 400,
  "title": "Invalid Query Parameter",
  "detail": "The filter query is not valid.",
  "errors": [
      {
          "code": "MINLENGTH",
          "path": "#/offset",
          "limit": 0
      }
  ]
  }