FLUME-247: Add Efficient HBase Sink whith Flexible Event's Attributes Writing
Please refer to the jira issue it has detailed explanation.

Added implementation of the sink and a simple test-case for it:
src/java/com/cloudera/flume/handlers/hbase/Attr2HBaseEventSink.java
src/javatest/com/cloudera/flume/handlers/hbase/TestAttr2HBaseSink.java

Not included in a diff (because the patch is applicable to Patric's http://github.com/phunt/flume/tree/hbase_sink2 branch, not trunk):

--- a/src/java/com/cloudera/flume/conf/SinkFactoryImpl.java
+++ b/src/java/com/cloudera/flume/conf/SinkFactoryImpl.java
@@ -63,6 +63,7 @@ import com.cloudera.flume.handlers.endtoend.AckChecksumChecker;
 import com.cloudera.flume.handlers.endtoend.AckChecksumInjector;
 import com.cloudera.flume.handlers.endtoend.ValueDecorator;
 import com.cloudera.flume.handlers.hbase.HBaseEventSink;
+import com.cloudera.flume.handlers.hbase.Attr2HBaseEventSink;
 import com.cloudera.flume.handlers.hdfs.CustomDfsSink;
 import com.cloudera.flume.handlers.hdfs.DFSEventSink;
 import com.cloudera.flume.handlers.hdfs.EscapedCustomDfsSink;
@@ -143,6 +144,7 @@ public class SinkFactoryImpl extends SinkFactory {
 
       // experiemental
       { "hbase", HBaseEventSink.builder() },
+      { "attr2hbase", Attr2HBaseEventSink.builder() },
 
       // deprecated
       { "thrift", ThriftEventSink.builder() },