Miscellaneous renaming string fixes

* Fixes for readme files, help, errors, comments
* Includes the name change for the guest agent and
  the topic name in agent_remote.py.
* Changes default config file to /etc/sahara/sahara.conf
  in sahara_api.py
* Change log and i8ln strings to 'sahara'
* Change project string in CONF object to 'sahara'

Partial-Implements: blueprint savanna-renaming-service
Change-Id: Ic353a013a0c7bb76f6724590bf1f558f6aafbede
Merge "Miscellaneous renaming string fixes"