XWIKI-11111: Create a list of icons that XWiki supports in the Icon Themes.
XWIKI-11530: Icon Theme configured in the preferences is loaded with a bad name.
XWIKI-11388: Create an icon picker that lists all available icons.
XWIKI-11361: Set of icons by default in AWM.

Todo: change the hint of the field to not display anymore a link to the silk gallery.