[INTERNAL] replaced Eclipse IFile usage with DPP IFile in OPN

Change-Id: I8597efa0f04fe7b7ada0cac872bff7901314d528
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1804
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>