Bulma minireset (https://github.com/jgthms/bulma/blob/master/sass/base/minireset.sass) was applied everywhere in iTop. This was causing HTML content without any Bulma or iTop 3.0.* CSS classes to render with no styles anymore, not even the default browser's ones. Especially rendering for content styled in CK Editor was problematic...
This commit creates a new `ibo-is-html-content` CSS class (in css/backoffice/utils/helpers/_misc.scss) that just extends the `content` Bulma class (indirection to reduce framework coupling).
This new iTop CSS class is added in :
* AttributeText and its children when format is HTML
* HTML components
* activity entries in HTML format
The class can also be used elsewhere when needed, for example in modules having custom pages that aren't using yet the iTop 3.0.* UI components or CSS classes.
