!!whiteboard

In order to let it be implemented in a plugin I had to modularize the tests leading to the display or not of the [edit] and [delete] buttons.
plugins can now provide css files which will be concatenated
an icon now shows that a message is a whiteboard
removal of useless console.log
fixed a bug preventing the display of the 'reply' button
changed message rendering management so that messages can be rendered differently by plugins if they're not in #messages or if they're updated