[REFACTOR] renamed getConfigPref methods in Saros class

The Javadoc is already talking about GLOBAL preferences to there is no
reason that the method names should not reflect them.

Change-Id: Idc4e8c28d9cd09e7ceed0e3abd6aafb93bbcf97e
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1238
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>