More retina support

[Adrien Crivelli]

Investigate the replacement of all background-size: contain with object-fit: contain and proper <img> tag in order to leverage <img [naturalSrcDensity]="'/api/image/123/200'" />.

So more or less:

- <div style="background-size: contain; background-image: '/api/image/123/200' ">
+ <img style="object-fit: contain;" [naturalSrcDensity]="'/api/image/123/200'">