Support gradual increase learning rate and SequentialSchedule in learningratescheduler (#2093)
Support gradual increase learning rate and SequentialSchedule in learningratescheduler (#2093)

* support SequentialSchedule and WarmupSchedule
yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL