Active photo in the editor to the left of the film streap

[carafife]

In rawtherappe when editing an image, the thumbnail synchronized by the "X" key is found in the middle of the banner. Under ART it is always placed on the left (see screenshots)

[agriggio]

filebrowser: center thumb in the film strip when syncing with the editor

Fixes #25

→ <<cset 049d13415896>>