[JTourBus] Expanded the "Activity Sending"-Tour

Added informations about the client-server-architecture to the "Activity
Sending"-Tour.

Change-Id: Ib5d28e48056e54e56ca5902ae79cc7542d842581
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1177
Tested-by: Jenkins CI
Reviewed-by: Patrick Schlott <pschlottk@gmail.com>