Cleaned up single-node devstack.sh
Moved to master branch of devstack.

While this might not be the most stable, in the icehouse one the EC2 does not seem to work at all. The `exercises/euca.sh` fails.
Moved to 192.168.42.xxx network to avoid conflicts with local networks where routers assigns 192.168.1.xxx
Minor changes
Added multinode devstack deployment
Updated documentation