Spark-2447 : Spark on HBase

Add common solution for sending upsert actions to HBase (put, deletes,
and increment)

This is the first pull request: mainly to test the review process, but there are still a number of things that I plan to add this week.

1. Clean up the pom file
2. Add unit tests for the HConnectionStaticCache

If I have time I will also add the following:
1. Support for Java
2. Additional unit tests for Java
3. Additional unit tests for Spark Streaming
You shouldn't specify versions in the children poms. In fact, you can't, since this one in particular has to be overridden by `hadoop.version`. You can remove all `<version>` in this file. In fact there is already an `hbase.version` defined in the parent, which affects the code examples. You may also have to harmonize the examples with the newer HBase.