Replace AsyncHBaseClient with HBase 2 client libraries

[stoty]

AsyncHBaseClient reimplements the HBase 1.x wire protocol to provide asynchronous interface.

HBase provides and asynchronous API since 2.0.
It has also added a lot features like encryption and alternate registries that simply do not work with AsyncHBaseClient.

Using the official client libraries would improve compatibility with HBase, and remove the need to maintain a separate client implementation.