wip #300 - Moved Java API class to japi subpackage, renamed CassandraJavaRow to CassandraRow under japi, japi.CassandraRow is now a regular class; extracted common portion of CassandraRow to AbstractRow; added tests for new CassandraRow class
wip #300 - renamed columnCount -> requiredColumns and consecutiveColumns -> consumedColumns in RowReader