[JTourBus] Added the Architecture Overview Tour

Added a JTourBus-Tour corresponding to the Architecture Documentation on
the Saros-Homepage. The Tour is intended to give an overview about
important Components and Interfaces used in Saros. It also makes
references to other, more detailed Tours on certain subjects.

Change-Id: I0a6750c23d86d22419096d5ea8e4504e87682567
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1176
Tested-by: Jenkins CI
Reviewed-by: Patrick Schlott <pschlottk@gmail.com>