ECMS-6013: HTM Lists not well displayed in exo content.

Fix description:
- Define explicitly HTML style to avoid unexpected overridden css

Conflicts:
	apps/portlet-presentation/src/main/webapp/skin/SingleContentViewer/DefaultSkin/Stylesheet.css
	apps/resources-wcm/src/main/webapp/skin/DefaultSkin/WCMStylesheet.css
	apps/resources-wcm/src/main/webapp/skin/DefaultSkin/webui/UITreeJCRExplorer/Stylesheet.css