Allow multiselect via ctrl in list

[jdittrich]

Currently, the photo list looks like this:

It should be possible to select several files with Ctrl.

This should be signified with a little note like "select multiple by keeping ctrl pressed"

On top or instead of this area

Should be a Text like "you selected 20 images"

In this area:

Would be multiple thumbnails OR no image at all.

If in some of the images, the geolocation can't be written, there should be a dialog saying "You tried to add a location to 20 images. Location was added to 18 of them. For 2 images, no location could be added because reason [if possible]:
[list of offending images]