Define HBase module public API and adjust visibility accordingly

First go at https://issues.cloudera.org/browse/CDK-112. Note that I've moved the public API into the com.cloudera.cdk.data.dao package, but I'm not fixed on that name. Also I haven't moved that package into the Data module yet.

If you run 'mvn site' from the top-level you will see the grouping of the HBase API. Still a few fixes needed, but this shows the general direction.