additionally loaded the message status icons smaller and (visually) hid
the vertical scrollbars (they can still be used, but cannot be seen).
Lastly checked all context menu functions for a NullPointerException, as
also no element can be selected when the context menu is created.
additionally added:
- the label on top of the ChatScene now displays the own users name
- the messageList now scrolls to the bottom when a message is
created/received