Admin: Enable logo changes with custom styles - refs #5578

[christianbeeznest]

No description provided.

[ywarnier]

This works but it should be inside the "colors" page. Otherwise you're not sure which CSS theme you're modifying with logos.
In my case I created a new theme, saved it, then went to "Branding", deleted the default logos, uploaded mine, and then my logo was in place of the default style in the var/themes/chamilo/images/ folder. It should have been saved in var/themes/[mytheme]/images/