dragging the non-panoramic photos should ease back to default position

[angelday]

Releasing the mouse currently leaves the photo in a weird position and we should smoothly ease back to where it was before.

[angelday]

@oscarlorentzon let me know when you're at this issue and we can discuss it in more detail

[angelday]

I discussed with @oscarlorentzon and we both agreed what it should work like (basically we both meant the same thing all along).