[SPARK-14279][BUILD] Pick the spark version from pom

## What changes were proposed in this pull request?
Change the way spark picks up version information. Also embed the build information to better identify the spark version running.

More context can be found here : https://github.com/apache/spark/pull/12152

## How was this patch tested?
Ran the mvn and sbt builds to verify the version information was being displayed correctly on executing <code>spark-submit --version </code>

![image](https://cloud.githubusercontent.com/assets/7732317/15197251/f7c673a2-1795-11e6-8b2f-88f2a70cf1c1.png)

Author: Dhruve Ashar <dhruveashar@gmail.com>

Closes #13061 from dhruve/impr/SPARK-14279.