DRILL-3262: Rename DrillDatabaseMetaData -> DrillDatabaseMetaDataImpl.
Renamed org.apache.drill.jdbc.impl.DrillDatabaseMetaData to
org.apache.drill.jdbc.impl.DrillDatabaseMetaDataImpl (re creating
org.apache.drill.jdbc.DrillDatabaseMetaDataImpl for DRILL-3198).
[DrillDatabaseMetaData -> DrillDatabaseMetaDataImpl, DrillJdbc41Factory]
