Removed use of 'common.utility.make_dict_proxy_wrapper' (previously used to make an OpenStack instance look like a dictionary) as it is no longer needed: an instance of OpenStack's openstack.compute.v2.server.Server class can now be used as dictionary as its parent class (i.e., the openstack.resource.Resource class) implements the mapping protocol.

Core: small optimization (avoid looking for measure sinks if the configuration parameter is an empty string)

GCP: added class to use for implementing synchronized operations (e.g., for waiting until the starting of an instance is done)

AWS: added class to use for implementing synchronized operations (e.g., for waiting until the starting of an instance is done)

GCP: modeling zones and regions as location. Core: moved some UI-related code into a separate module

GCP: now support both 'OAuth2 Client ID' and 'Service Account' authentication strategies; also, refactored some GCP's class to reduce code duplication

Major change: all classes are now confined in the 'easycloud' namespace. Also, fixed some minor bugs.