Removed a volume dir in Dockerfile

Updated image size in README

Renamed CHEF_PORT to SSL_PORT

SSL_PORT will default to 443 when missing
Renamed validation_client_name
Updated README

consolidate VOLUME in Dockerfile

Container improvements

- The SSL certificate will be named 'chef-server.crt' by default
- Disabled non SSH traffic (HTTP requests to SSL port will fail)
- Moved all the Chef configuration commands out of 'run.sh'

Chef Server 12 is now supported

- The container won't reconfigure Chef after a reboot
- Better logging
- Removed unused commands

- Enforce Chef Server 11 (instead of lastest Chef Server version)

- Reduced image size (From 1.319GB to 1.025GB)