Add a message center field

[Akron]

Messages from the information method in Kalamasr are only shown briefly at the right bottom corner and then disappear. The same is true for rewrite information on the corpus or query objects. These messages should be collected and made accessible via a single field, similar to the news center in Windows. The button may be placed anywhere in the UI and only appears, when a warning, a rewrite or something else appears in the KoralQuery response or issued by the Kalamar client code. A click on the button opens a view of the collected messages, maybe embedded like the embedded documentation.