Various improvements to P4 tutorial

- Added steps to exercise 2 to use wireshark to capture MyTunnel packets
- Various formatting fix/improvements
- Fixed markdown link to use relative paths
- Fixed bm-cli command not to use sudo (not needed)

Change-Id: I514da99a6cfadd048294c610ba201503c0339e89
(cherry picked from commit 19ea89f8540eef0e41fdf7b4fd9a2a1950f2ade9)
diff --git a/tools/dev/p4vm/bm-commands.sh b/tools/dev/p4vm/bm-commands.sh
index 599f5c0..ba69f77 100644
--- a/tools/dev/p4vm/bm-commands.sh
+++ b/tools/dev/p4vm/bm-commands.sh
@@ -7,7 +7,7 @@
     fi
     tport=$(head -n 1 /tmp/bmv2-$1-thrift-port)
     echo "Starting CLI for BMv2 instance $1 (Thrift port $tport)..."
-    sudo bm_CLI --thrift-port ${tport} --pre SimplePreLAG ${@:2}
+    bm_CLI --thrift-port ${tport} --pre SimplePreLAG ${@:2}
 }
 
 bm-dbg () {