Data Packaging: Mark incomplete observations as complete when new observations have started for that stream id

[kmharrington]

Right now we only mark observations as complete if there are end of observations frames in the files. But these aren't written when the system crashes.

We've just been fixing these by hand, but one way to fix these automatically would be to stay "if that slot has started streaming again then the previous observation must be over." This would reduce the number we would need to fix by hand significantly