Revert "[INTERNAL] Remove deprecated and unused method from ITransmitter"

This reverts commit e48b02098e4975b6816fe1edcd91a91cbdd33a73.

The Whiteboard does not use a Server-Client architecture as far as I can 
remember, so this patch may break the functionality to use the Whiteboard
with more than 2 users.

Change-Id: I45315601cd0b023675df4e3990d6796ef890b7ba
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1475
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>
Tested-by: Jenkins CI