This is a crontab service that supports hot plug and high performance. In addition, it supports second level (first parameters), multi time point and time section function.
这是一个支持热插拨、高性能的crontab服务，另外，它还支持秒级别（第1个参数）、多时间点、时间段功能。
// six columns mean：
// second：0-59
// minute：0-59
// hour：1-23
// day：1-31
// month：1-12
// week：0-6（0 means Sunday）
// SetCron some signals：
// *： any time
// ,： separate signal
// －：duration
// /n : do as n times of time duration
/////////////////////////////////////////////////////////
// 0/30 * * * * * every 30s
// 0 43 21 * * * 21:43
// 0 15 05 * * * 05:15
// 0 0 17 * * * 17:00
// 0 0 17 * * 1 17:00 in every Monday
// 0 0,10 17 * * 0,2,3 17:00 and 17:10 in every Sunday, Tuesday and Wednesday
// 0 0-10 17 1 * * 17:00 to 17:10 in 1 min duration each time on the first day of month
// 0 0 0 1,15 * 1 0:00 on the 1st day and 15th day of month
// 0 42 4 1 * * 4:42 on the 1st day of month
// 0 0 21 * * 1-6 21:00 from Monday to Saturday
// 0 0,10,20,30,40,50 * * * * every 10 min duration
// 0 */10 * * * * every 10 min duration
// 0 * 1 * * * 1:00 to 1:59 in 1 min duration each time
// 0 0 1 * * * 1:00
// 0 0 */1 * * * 0 min of hour in 1 hour duration
// 0 0 * * * * 0 min of hour in 1 hour duration