Kepler

This bug implements the feature to retrieve the last timestamp for which a sensor's data was stored in metacat. For each sensors, the data is stored in the metacat. We need to keep track of the timestamp of the last data for the sensor that was stored in the metacat. At current, we are proposing to store this information in a database (mysql). Table sensorTimeInfo(sensorId, lastTime) which will keep updated with the last timestamp for each sensor which the data has been stored in the metacat.