[FEATURE] Offline VISTA images

[virajkaram]

We should download VISTA images and store them offline, similar to what we did for UKIRT. We don't need all of them, just dec>-35 should be good (images further south can be queried from the online server if required).

This will also help figure out which images are deprecated, there is no way of doing this currently until astroquery make some changes on their end - astropy/astroquery#2809.