[MAJOR] session-counters: split FE and BE track counters

Having a single tracking pointer for both frontend and backend counters
does not work. Instead let's have one for each. The keyword has changed
to "track-be-counters" and "track-fe-counters", and the ACL "trk_*"
changed to "trkfe_*" and "trkbe_*".
diff --git a/include/types/proto_tcp.h b/include/types/proto_tcp.h
index a7ca56a..bee52aa 100644
--- a/include/types/proto_tcp.h
+++ b/include/types/proto_tcp.h
@@ -32,7 +32,8 @@
 enum {
 	TCP_ACT_ACCEPT = 1,
 	TCP_ACT_REJECT = 2,
-	TCP_ACT_TRK_CTR = 3,
+	TCP_ACT_TRK_FE_CTR = 3,
+	TCP_ACT_TRK_BE_CTR = 4,
 };
 
 struct tcp_rule {