Add README file for the protable foundation infra directory.

Signed-off-by: Liming <mistersky@gmail.com>
Add the Container Provisioning Agent (CPA) script, RESTconf
server host_pf_server.py on host hosting the forwarding elements,
reference client to access the RESTconf server from within the
portable foundation, a sample UDI_DB.json storing the local
configs for the portable foundations supported on local host.
And an updated README file.

Signed-off-by: Liming <mistersky@gmail.com>
Merge changes I6fff0f07,I4c569990

* changes:
  Add the Container Provisioning Agent (CPA) script, RESTconf server host_pf_server.py on host hosting the forwarding elements, reference client to access the RESTconf server from within the portable foundation, a sample UDI_DB.json storing the local configs for the portable foundations supported on local host. And an updated README file.
  Add README file for the protable foundation infra directory.