Preparation for 20s cadence

[rhandberg]

In the preparation of 20s cadence data we have a couple of things that needs to be addressed:

• [ ] Cadence in seconds should be stored in the TODO-lists, to help distinguish 120s and 20s TPFs from each other. This also means that the following steps in the pipeline (data validation and corrections) should used this instead of datasource.
• [x] Detections of cosmic rays. For 20s cadence there will not be any cosmic ray mitigation (on board the spacecraft and likely on ground), so we need to look into detecting cadences where the stamps were hit by cosmic rays.

[rhandberg]

Cosmic ray mitigation will be handled by SPOC, and therefore we don't have to put special attention to this.