Added 'stop' functionality to ec2 driver

Added new state, added stop method, removed alias.
Added start functionality to stopped EC2 instances
Fixed instance state conversion. Tested EBS instance for start/stop/reboot. Works fine
Fixed formatting
Modified 'stop_instance' method to check if instance root type is ebs or instance_store. If ebs -- stop instance otherwise destroy instance
Cleaned up code
Added note
EC2 driver - modify instance actions depending on transient root (ebs/root_store)

related to https://github.com/deltacloud/deltacloud-core/pull/44
EC2 driver - Fix for determining instance_actions on ebs/root_store instances

https://github.com/deltacloud/deltacloud-core/pull/47