Fix/sort datetime

[GoOz]

• [x] Fix sorting by month that was still relying on created_at instead of metadata.datetime
• [x] Cleaning remaining occurrence of created_at
• [x] Updated tests

[GoOz]

(1) [PHO-18] Trier les photos par date de prise de vue et pas par date de création

[GoOz]

Travis is failing because tests are broken with another component. Waiting for this component to be updated before rebasing.