[REEF-45]: Use consistent STDOUT and STDERR file names in the local runtime

  This updates the local runtime to use the correct file names for STDOUT and
  STDERR redirection as provided by the REEFFileNames class.

JIRA:
  [REEF-45] https://issues.apache.org/jira/browse/REEF-45

Author:    Markus Weimer <weimer@apache.org>

Closes #20