ONOS-6457 Improved bmv2.py mininet script

- Starts BMv2 with empty.p4 as when running with --no-p4 the switch
  crashes
- Automatically send a netcfg JSON to ONOS for each device
- Makefile to build all P4 programs (needed for empty.p4)

Change-Id: Ib872641751c543aac6c752610b1ce88a1a00d0d2
diff --git a/tools/test/p4src/p4c-out/.gitignore b/tools/test/p4src/p4c-out/.gitignore
new file mode 100644
index 0000000..f02ec97
--- /dev/null
+++ b/tools/test/p4src/p4c-out/.gitignore
@@ -0,0 +1,2 @@
+*.json
+*.p4info
\ No newline at end of file