[REFACTOR] renamed ChatDisplay class

Renamed to SkypeStyleChatDisplay to reflect the style/layout that this
class is trying to display.

Change-Id: I9d143f7c80e644cd5563b287cd74e8db8725b465
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1906
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>