[SPARK-1776] Have Spark's SBT build read dependencies from Maven.

Patch introduces the new way of working also retaining the existing ways of doing things.

For example build instruction for yarn in maven is
`mvn -Pyarn -PHadoop2.2 clean package -DskipTests`
in sbt it can become 
`MAVEN_PROFILES="yarn, hadoop-2.2" sbt/sbt clean assembly`
Also supports
`sbt/sbt -Pyarn -Phadoop-2.2 -Dhadoop.version=2.2.0 clean assembly`


Here it might be nice to echo back to the user that you've converted their strings into a new option:

```
NOTE: Setting SPARK_YARN is deprecated. Use the `-Pyarn` flag.
NOTE: Setting SPARK_HADOOP_VERSION is deprecated. Use `-Dhadoop.version=XX`.
```