Feedback messages and Admin message should be closable

Allow to quickly close the feedback messages (when we don't need / want to wait for the timeout before clicking on something that's hidden by the message, for instance the actions in DAM).

Closing it by:

• clicking on it
• clicking on a 'close' link
• ...

We have 4 types of messages:

• status messages: currently not closable, only displayed during N seconds (draft saved, document created, etc)
• status messages with links: displayed permanently until the user answers the question / does the action (restore? Yes / No or You should restart your server -> restart button)
• administrator message: not closable, displayed permanently until the admin remove it
• chrome frame message: closable, displayed permanently until the user close it

Since all the messages should be closable, we could think about having only one type of messages + parameters to chose:

• the display time (permanently / temporarily)
• the styles (info, warning, success, error, admin)
• maybe the position ( default like status messages, center, bottom, … It can be handled by a secundary css class)

If the user puts the cursor on the message the temporarily messages should stay visible until:

• he move the cursor outside the message box
• he close the message by clicking on the X button or a link (status messages with links)