DataSets should update DataSetViews even if they aren't playing

[Dan Garner]

This would be an extension to the "pre-cache" work we have already done. The DataSet would push a "last modified date" down to the resource node in required files.

If present, each client would use this to determine if an update of that Data Set View is necessary.

[Dan Garner (dangarner)]

The CMS part of this is done.

[Dan Garner (dangarner)]

Windows client part of this is done.

[Dan Garner (dangarner)]

When updating the watermark we should also ping the display records and mark their required file status as invalid.

[Dan Garner (dangarner)]

Done last CMS comment.

Will assign to Alex for Python client alterations.

Required Files contains a new field called "updated" which is the unixtime stamp that resource was last updated on the server. When deciding whether to download the file the client should look at that stamp and compare it to the last write time on the file.

If the last write time is before the stamp, then download the file.

This means data sets update without them being the in the schedule (they just need to be within required files).