Certification Required page:
* Show helpful advice if the reason for the page is only that the user had
deleted their default profile pic, but their account was certified.
Batch Photo Delete & Visibility:
* On user galleries, owners and admins can batch Delete or Set Visibility on
many photos at once. Checkboxes appear in the edit/delete row of each photo,
and bulk actions appear at the bottom of the page along with select/unselect
all boxes.
* Deprecated the old /photo/delete endpoint: it now redirects to the batch
delete page with the one photo ID.
Misc Changes:
* Notifications now sort unread to the top always.
