Save all pictures offline

A way to save pictures offline by bulk would be nice. This for cache pictures but optionally also for log pictures.

Currently based on my knowhow this is only possible when I'm online to scroll through the picture list and wait till each and every picture is cached. After that it's still available when I'm caching and do not have a mobile reception. 

I would see this feature at two locations within the app:

In the picture view of a cache:

- Download cache pictures for offline usage

- Download all pictures for offline usage

In the cache list based on the current filter (similar to refresh cache data):

- Download cache pictures for offline usage of all shown caches

- Download all pictures for offline usage of all shown caches

Would be nice if this feature would be considered