Add support for direct meters in generating P4 constants

Also, add imports for PI IDs only when needed in the constants file.

Change-Id: If1821a55a07d5f6874514174381be212188580e3
diff --git a/pipelines/fabric/impl/src/main/resources/Makefile b/pipelines/fabric/impl/src/main/resources/Makefile
index 11cdba9..12e53d7 100644
--- a/pipelines/fabric/impl/src/main/resources/Makefile
+++ b/pipelines/fabric/impl/src/main/resources/Makefile
@@ -24,7 +24,7 @@
 ifndef ONOS_ROOT
 	$(error ONOS_ROOT is undefined)
 endif
-	docker run -v $(ONOS_ROOT):/onos -w /onos/tools/dev/bin \
+	docker run --rm -v $(ONOS_ROOT):/onos -w /onos/tools/dev/bin \
 		--entrypoint ./onos-gen-p4-constants opennetworking/p4mn:stable \
 		-o /onos/pipelines/fabric/api/src/main/java/org/onosproject/pipelines/fabric/FabricConstants.java \
 		fabric /onos/pipelines/fabric/impl/src/main/resources/p4c-out/fabric-full/bmv2/default/p4info.txt