added 3 bmv2 examples: copy_to_cpu, meter, TLV_parsing

examples/README.md

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+# P4 Code Samples
+
+## Introduction
+
+This directory includes P4 code samples, meant to be run on bmv2, which
+illustrates several more advanced features of P4. The following samples are
+included:
+
+- `copy_to_cpu`: how to use the `clone_ingress_to_egress primitive` to clone the
+  packet, encapsulate it and send it to a special port.
+- `meter`: how to use indirect meters in P4.
+- `TLV_parsing`: how to parse IPv4 options
+
+All examples are orgranized the same way, with a `p4src` directory containing
+the P4 source code, and a `README` file describing the P4 program and explaining
+how to run a quick demonstration.
+
+## Obtaining required software
+
+To complete the exercises, you will need to clone 2 p4lang Github repositories
+and install their dependencies. To clonde the repositories:
+
+- `git clone https://github.com/p4lang/behavioral-model.git bmv2`
+- `git clone https://github.com/p4lang/p4c-bm.git p4c-bmv2`
+
+The first repository ([bmv2](https://github.com/p4lang/behavioral-model)) is the
+second version of the behavioral model. It is a C++ software switch that will
+behave according to your P4 program. The second repository
+([p4c-bmv2](https://github.com/p4lang/p4c-bm)) is the compiler for the
+behavioral model: it takes P4 program and output a JSON file which can be loaded
+by the behavioral model.
+
+Each of these repositories come with dependencies. `p4c-bmv2` is a Python
+repository and installing the required Python dependencies is very easy to do
+using `pip`: `sudo pip install -r requirements.txt`.
+
+`bmv2` is a C++ repository and has more external dependencies. They are listed
+in the
+[README](https://github.com/p4lang/behavioral-model/blob/master/README.md). If
+you are running Ubuntu 14.04+, the dependencies should be easy to install (you
+can use the `install_deps.sh` script that comes with `bmv2`). Do not forget to
+build the code once all the dependencies have been installed:
+
+- `./autogen.sh`
+- `./configure`
+- `make`
+
+## Before starting the exercises
+
+You need to tell us where you cloned the `bmv2` and `p4c-bm` repositories
+:). Please update the values of the shell variables `BMV2_PATH` and
+`P4C_BM_PATH` in the `env.sh` file - located in this directory. Note that if you
+cloned both repositories in the same directory as this one (`tutorials`), you
+will not need to change the value of the variables.
+
+You will also need to run the `veth_setup.sh` script included in this directory
+as `sudo` to setup the veth interfaces needed by the switch.
+
+That's all :)