Example code reorg and auth examples

A slight reorganization on the example code to avoid conflicts
and make it clearer how to use the example code:
* Move transport code out of common.py to transport.py
* Try to keep example code in silos of functionality to avoid
  conflicts (transport.py, authenticate.py, ...)

For the authentication examples:
* Added basic identity v2 and v3 authentication command

To run:
python -m examples.authenticate
python -m examples.transport https://region-a.geo-1.identity.hpcloudsvc.com:35357/

Change-Id: I3f342409a7df645bfed82963488b665e1fb191e7