Handle HBase namespaces in Atlas reporting task

NiFi's Atlas reporting task creates hbase_table entities in Atlas from events generated by different HBase processors. The hbase_table Atlas entity has a reference to hbase_namespace which was optional earlier but it is mandatory from Atlas 2.1 on.

Implement handling hbase_namespace entities in NiFi. Creation of hbase_table currently fails due to the missing namespace entity.

Screenshots of sample entities generated with Atlas' HBase Hook attached (as a reference for filling the properties in properly).