veyron/security/agent: Make the agent a pricipal.

* The private key for the principal will have to be in a file named
privatekey.pem located in the directory VEYRON_CREDENTIALS.
* Agent server will have a underlying pricipal.
* Agent client makes rpcs to server to act as a principal.

Change-Id: I29d69c0bfbae4ef3c7530f6a4636b304d56c9cf3
11 files changed
tree: 7886e7d601301be3ce175315c0d1451402045f50
  1. lib/
  2. profiles/
  3. runtimes/
  4. security/
  5. services/
  6. tools/