Replace uses of Whirr with supported tooling

[Apache Whirr](http://whirr.apache.org/) has been retired; however, we have several uses of Whirr in the docs:

* [`docs/hbase.txt`](https://github.com/JanusGraph/janusgraph/blob/ec441ac6d87f3359c9740075786ec6de3651745e/docs/hbase.txt)
* [`janusgraph-hbase-parent/common/test/conf/whirr-hbase.properties`](https://github.com/JanusGraph/janusgraph/blob/22f584d45d602e4d631ecc8a30f90c4be9f3ffcf/janusgraph-hbase-parent/common/test/conf/whirr-hbase.properties)
* [`janusgraph-cassandra/config/whirr-cassandra.properties`](https://github.com/JanusGraph/janusgraph/blob/ec441ac6d87f3359c9740075786ec6de3651745e/janusgraph-cassandra/config/whirr-cassandra.properties)

These should all be removed and replaced with a modern, supported deployment tool, of which there are many (e.g., Chef, Ansible, Puppet, Salt, Terraform, etc.).