java_gen: small improvements to gen_table/tlv extensions

 - move bsntlv classes to dedicated package/factory
 - change type of of_bsn_tlv_vlan_vid to VlanVid
 - change type of tableId to new typesafe constant GenTableId
diff --git a/test_data/of13/bsn_gentable_entry_stats_reply.data b/test_data/of13/bsn_gentable_entry_stats_reply.data
index cd4ab62..255de88 100644
--- a/test_data/of13/bsn_gentable_entry_stats_reply.data
+++ b/test_data/of13/bsn_gentable_entry_stats_reply.data
@@ -60,20 +60,20 @@
         ImmutableList.<OFBsnGentableEntryStatsEntry>of(
             factory.bsnGentableEntryStatsEntry(
                 ImmutableList.<OFBsnTlv>of(
-                    factory.bsnTlvPort(OFPort.of(5))
+                    factory.bsnTlvs().port(OFPort.of(5))
                 ),
                 ImmutableList.<OFBsnTlv>of(
-                    factory.bsnTlvRxPackets(U64.of(100)),
-                    factory.bsnTlvTxPackets(U64.of(101))
+                    factory.bsnTlvs().rxPackets(U64.of(100)),
+                    factory.bsnTlvs().txPackets(U64.of(101))
                 )
             ),
             factory.bsnGentableEntryStatsEntry(
                 ImmutableList.<OFBsnTlv>of(
-                    factory.bsnTlvPort(OFPort.of(6))
+                    factory.bsnTlvs().port(OFPort.of(6))
                 ),
                 ImmutableList.<OFBsnTlv>of(
-                    factory.bsnTlvRxPackets(U64.of(100)),
-                    factory.bsnTlvTxPackets(U64.of(101))
+                    factory.bsnTlvs().rxPackets(U64.of(100)),
+                    factory.bsnTlvs().txPackets(U64.of(101))
                 )
             )
         )