[GUI] Move option for contribution annotations to appearance page

The option for showing the contributions of other session participants
was moved from the AdvancedPreferencePage to the
AppearancePreferencePage, where it fits better. The former name tag
group on the AppearancePreferencePage was renamed to Annotations.

Copied from SWTP-2013 repository.
 - Commit 7f478bc
 - Reviewed on: http://saros-build.imp.fu-berlin.de/gerrit/1059
 - Reviewed by: Richard Möhn <richard.moehn@fu-berlin.de>
 - Reviewed by: Christoph Krüger <chistoph.krueger@fu-berlin.de>

Change-Id: Iad3b8dcd51058d6c5efd21704dc31999c49b7303
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1230
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>