Add documentation on how to use the hbase10 client with Google's
Bigtable.

Fix broken synchronization meant to guard against over-creation
of cluster connection instances on startup when multiple threads.

object. Previously N objects were instantiated because the method didn't
check to see if the connection was null.

- define checkstyle configs in as few places as possible
- use checkstyle:check since it has defaults that match what we want (fail after logging to console)
- modules that have current failures set property checkstyle.failOnViolation to false.

[cassandra cassandra2 dynamodb hbase098 hbase10 jdbc s3] Fixing squid:S1481 - Unused local variables should be removed

Replaces numeric status codes with a canonical set of Status objects,
each with a short name and description.
Bindings with more specific errors (e.g., timeouts) return additional
statuses.

This changes the default output from messages like:

   [UPDATE], Return=0, 511

To:

   [UPDATE], Return=OK, 511

Fixes #438

Via `hbase.usepagefilter`

Other bindings limit the number of results retrieved from the server.
The HBase bindings just close the scanner once they have received the
desired number of records. Adding a PageFilter matches the behavior of
other bindings, and may improve performance.

Uses an HBase mini-cluster to test the HBase binding.

Remove deprecated methods:
Put.add -> Put.addColumn.
KeyValue -> Cell.

HBase 0.94 requires an additional dependency on hadoop-core, but has no
source-level changes to the client.