[INTERNAL] cleaned up ChatControl

Made fields private and / or final. Moved all private methods to the
bottom and all public methods to the top.

Change-Id: I893fc9f488f0fa76a3dda87892fd360e7051a562
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1904
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>