Generate and display ssh public key fingerprints instead of key contents

Trello Card: https://trello.com/c/iB213gUS/8-show-individual-ssh-key-fingerprints-in-the-console

Updated files:
modified:   console/app/models/key.rb
modified:   console/app/views/settings/_keys.html.haml

Updated to generate ssh key fingerprint in the model, and display that fingerprint in the view instead of the content of the key
Type should not be included in the fingerprint since we support other types of keys like kerberos principals.  Take a look at rhc to see what is fingerprinted and what isnt.  There is a helper method on the models/key.rb for is_ssh?