- When a resourceOffers() call has multiple offers, force the TaskSets
  to consider them in increasing order of locality levels so that they
  get a chance to launch stuff locally across all offers

- Simplify ClusterScheduler.prioritizeContainers

- Add docs on the new configuration options

Also build and copy ML Lib scaladoc in Spark docs build.
Some more minor cleanup with respect to naming, test locations etc.

Consistently invoke bash with /usr/bin/env bash in scripts to make code more portable (JIRA Ticket SPARK-817)

These typos were reported on the spark-users mailing list, see: https://groups.google.com/d/msg/spark-users/SyLGgJlKCrI/LpeBypOkSMUJ

Conflicts:

	core/src/main/scala/spark/SparkContext.scala

1) Add support for HADOOP_CONF_DIR (and/or YARN_CONF_DIR - use either) : which is used to specify the client side configuration directory : which needs to be part of the CLASSPATH.

2) Move from var+=".." to var="$var.." : the former does not work on older bash shells unfortunately.