Add file sort for last created annotations

[lehecht]

Add a new file sort to the volume overview, where files are sorted by their latest annotation.

Closes #477.

[mzur]

Ready for review?

[mzur]

Please implement an API endpoint that returns the timestamps for the images instead of passing them on to the view every time. This could be a lot of data if the volume is large and it could be unnecessary data if the sorter is not used. The getSequence() method of the sorting component already returns a promise so taking the result of an API request here should work out of the box.

Also you should implement getting the timestamps for each file in a single database query (hint: combine groupBy with max). Currently you fetch all annotations of the entire volume and this could be literally hundreds of thousands.