Allow users to upload images to their WriteFreely instance.
Users should be able to:
- Upload photos while composing a post in the web interface (T659)
- View a library of their photos on a new Photos tab
- Add a caption to each photo in their library, stored in the database
- Store image size, original filename, and upload date for each photo in the database
- Delete photos in their library
Admins should be able to: