Normalised MAS timestamps

[edisonguo]

Since we turned on timestamp extraction from MAS, this has caused problems with WOfS not returning discrete days because the underlying timestamps aren't uniformly distributed. Currently we have two timestamp generation mechanisms:

• Timestamps are generated using start, stop and step values manually provided in the configuration file.

• Exact timestamps are returned from MAS.

We need a third option: timestamp start/stop range is taken from MAS but the timestamps returned to the client are uniformly generated using the step value.