admin audit panel: fix security entry presentation when object has been deleted
actions: add automatic css class: "action", "action-category", "action-category-name"

this allows easier styling of all actions, actions for a category, or a
single one
action icon: added DynamicIcon, to use an image with a computed url

use case: user avatar
add view for user avatar; add css class "avatar"
authenticated user group action: show user avatar instead of generic icon