Add analysis to show image capture timeline

[eric-czech]

Per #43, we will stick with inferring time 0 as the first timestamp for an image from an array. However, since the images are then grouped into buckets based on some time gap between them (1 hour by default) it will likely make sense to explicitly show what "hr X" means exactly for every array as well as how many images are associated and what absolute times they correspond to.

[eric-czech]

Note: This should be an analysis across all arrays. You can already get this information from the app but it requires selecting every array and recording the dates/counts in order to compare across them.