To prepare for video support
Migrate database rename tables and columns:
- photo to media
- photo_url to media_url
- photo_exif to media_exif
- Update api accordingly
This fixes#33 where a curtain image would cause the goexif2 library to
panic.
Now instead of crashing the entire program, it recovers and instead
prints an error to the console and ignores the EXIF data for that image.