add sbatch output file to sbatch script
Rename a number of files and environment variables to Magpie, including:

  hadoop-common-exports -> magpie-common-exports
  hadoop-post-run -> magpie-post-run
  hadoop-run -> magpie-run
  examples/hadoop-example-post-job-script -> examples/magpie-example-post-job-script
  examples/hadoop-example-pre-job-script -> examples/magpie-example-pre-job-script
  bin/hadoop-expand-nodes -> bin/magpie-expand-nodes
  hadoop.sbatch -> magpie.sbatch
  HADOOP_CLUSTER_NODERANK -> MAGPIE_CLUSTER_NODERANK
  HADOOP_PRE_JOB_RUN -> MAGPIE_PRE_JOB_RUN
  HADOOP_POST_JOB_RUN -> MAGPIE_POST_JOB_RUN
  HADOOP_SCRIPTS_HOME -> MAGPIE_SCRIPTS_HOME

Various cleanup/re-org was done b/c of this within the scripts and documentation
too.
tweak some text in README for clarification