Implementation of the alt and copyright fields in image views, that are returned by the JSON
Image: Don't need to add optional parameters

Fragments can only be created by the JsonParser, there is no need to
optional parameters. Keeping them could lead to confusion.
Image: Always define “alt” attribute

The <img /> tag should _always_ define an “alt” attribute, and there is
no reason for @alt to be nil, so we can always use it (in the worst
case, it will be empty).
Merge branch 'alt_copyright_in_image_views'