[INTERNAL] removed TextEditActivity data object class

With commit 724c6e4fd91aa947c6c465ba5a49eda035f7fb30
TextEditActivities are no longer serialized.

Removed all code parts that were using objects of this class.

Change-Id: Ie8e427acfb2978b0f934c5a8ebff6b56c9cf571e
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/846
Tested-by: Jenkins CI
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>
Reviewed-by: Patrick Schlott <pschlottk@gmail.com>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>