Refactored the OpenStack connector.
Refactored StratusLab connector.
Refactored CloudStack connector.
Merge branch 'master' into refactor/context_script_on_client
Minor. Code review updates.
Merge branch 'refactor/context_script_on_client'

Conflicts:
	cloudstack/jar/src/main/java/com/sixsq/slipstream/connector/cloudstack/CloudStackConnector.java
	openstack/jar/src/main/java/com/sixsq/slipstream/connector/openstack/OpenStackConnector.java