[INTERNAL] reintegrated Nebula back into Saros

Put back the code to Saros. This should make it easier to convert Saros
to another Widget Toolkit as the code is not "hidden" in a third
library. This patch also solves runtime issues that can
be made when the plugin references (versions) are not updated correctly.

Change-Id: I78352b28a1addb865c6e3cc4940e49fe918ffd1c
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1258
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>