* Adding initial implementation of basic_encap example
* Updated basic_encap example to count the number of valid packets
* Updated basic_encap example to put encapsulation layer after Ethernet
header.
* Added solution file for basic_encap example
* Changed the name of the basic_encap example to basic_tunnel and called
the new header myTunnel. Also changed the myTunnel field names slightly.
* Updated the README file for the basic_tunnel exercise. Also added topo.pdf
image to serve as a reference during implementation.
* Updated basic/README.md to point to basic_tunnel as the next exercise.
* Updated the README for basic to point to basic_tunnel.
Updated the starter code for basic_tunnel to look like basic
solution with todo comments.
Updated send.py and receive.py to be able to send both plain IP
packets and tunneled IP packets.
Updated basic_tunnel.p4 to have same control flow as p4runtime
exercise.
