Images display in the proper order when a narrative is played. A default image is displayed if the narratives has no images.
For now, the default image is just a random image taken from the internet.
Note: Right now the case where we have audio files 1, 2, 3, 4... but only image file 5.jpg is not handled properly (the default image is currently displayed).
Changes to admin_controller to respect the new pathname scheme.
Merge branch 'backend-dev' of https://github.com/felixsoum/youdeliberate into backend-dev