Custom Operator to accept Record as input

I really liked the Json Rules Engine. It would be good if record object is also pushed as input to operator so that one can compare relative value from the same Record using Json Path by introducing custom Operator in the engine. At present, there is not way to have Record object as operator input.

未指定檔案或測試。首先定位自訂運算子的評估路徑，以及其目前輸入的建構方式。完成的標準是：自訂運算子可以接收 Record 物件，並透過 Json Path 比較同一筆記錄中的值，同時為此行為提供涵蓋。

由索引模型根據 Issue 內容生成。