First stab at BNG support in fabric.p4

This implementation is derived from Deutsche Telekom contribution:
https://github.com/opencord/p4se

It supports basic upstream and downstream termination based on double
VLAN tags and PPPoE, including counters and downstream metering.

Change-Id: I940959f2338d7319654cf665f6cfe2de7200616b
diff --git a/pipelines/fabric/src/main/resources/.gitignore b/pipelines/fabric/src/main/resources/.gitignore
index 07ae761..fcd51a7 100644
--- a/pipelines/fabric/src/main/resources/.gitignore
+++ b/pipelines/fabric/src/main/resources/.gitignore
@@ -1,2 +1,3 @@
 p4c-out/*/tofino
 p4c-out/**/graphs
+p4c-out/**/_pp.p4