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_add.data b/test_data/of13/bsn_gentable_entry_add.data
index d8db0f8..02c2bb4 100644
--- a/test_data/of13/bsn_gentable_entry_add.data
+++ b/test_data/of13/bsn_gentable_entry_add.data
@@ -39,17 +39,17 @@
 -- java
 builder.setXid(0x12345678)
     .setChecksum(OFChecksum128.of(0xFEDCBA9876543210L, 0xFFEECCBBAA998877L))
-    .setTableId(20)
+    .setTableId(GenTableId.of(20))
     .setKey(
         ImmutableList.<OFBsnTlv>of(
-            factory.bsnTlvPort(OFPort.of(5)),
-            factory.bsnTlvMac(MacAddress.of("01:23:45:67:89:ab"))
+            factory.bsnTlvs().port(OFPort.of(5)),
+            factory.bsnTlvs().mac(MacAddress.of("01:23:45:67:89:ab"))
         )
     )
     .setValue(
         ImmutableList.<OFBsnTlv>of(
-            factory.bsnTlvPort(OFPort.of(6)),
-            factory.bsnTlvMac(MacAddress.of("ff:ee:dd:cc:bb:aa"))
+            factory.bsnTlvs().port(OFPort.of(6)),
+            factory.bsnTlvs().mac(MacAddress.of("ff:ee:dd:cc:bb:aa"))
         )
     )
 -- c