Make movie generation for low cadence dataset (SOHO, etc) more intuitive

[Keith Hughitt]

Currently, for datasets such as EIT 171 which may have only 1-3 images a day, the default "24 hour movie" does not work well and the user is often information that "insufficient data exists". Rather than do that, perhaps the user should be notified that there are only x images per day for the requested layer, and ask if they would like to make a ~1 week movie instead.