Extract metadata from images

The most important metadata values would be date of creation, location, device. Dimensions could be scanned as well, but not so useful. Date of creation would allow to sort images by true date and not date of modification. EXIF should be used.

No source files, tests, or entry points are named in the issue. Start by locating where images are imported and represented, then trace how their dates and other metadata are stored and used for sorting; done means EXIF creation date, location, and device metadata are extracted, with dimensions considered as described.

Written by the indexing model from the issue text.