整数のプロパティーの値
        Contains a valid value when propertyType is SerializedPropertyType.Integer.
          For accessing sbyte, byte, short, ushort, int and uint properties. If you are accessing long or ulong properties use longValue instead. 
 
          When assigning a value to intValue, the value is clamped in the range of the property's declared type. For example, a property that is declared as a byte is clamped between 0 and 255.
          See Also: longValue, propertyType, SerializedPropertyType.Integer.