Updates for p4runtime example (#71)

* Created p4runtime exercise directory with draft P4 program

* Updating VM

- Adding p4 to vboxsf group for VirtualBox Shared Folders
- Adding gRPC Python package for p4 runtime
- Setting up VM to use 2 CPUs

* Updating .gitignore for PyCharms and Mac OS

* Adding P4RuntimeSwitch type and support in run_exercises

If the grpc switch target is used, we will instantiate a P4RuntimeSwitch.
Ideally, this will get merged with BMv2's P4Switch and can be removed

* Adding p4 runtime and p4info browser libraries

Also, adding a Makefile for this project

P4D2_2017_Fall/vm/root-bootstrap.sh

@@ -67,6 +67,7 @@ useradd -m -d /home/p4 -s /bin/bash p4
 echo "p4:p4" | chpasswd
 echo "p4 ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/99_p4
 chmod 440 /etc/sudoers.d/99_p4
+usermod -aG vboxsf p4
 
 cd /usr/share/lubuntu/wallpapers/
 cp /home/vagrant/p4-logo.png .