Add Multi Cloud Capability to the Murano Core Library Classes

Today murano can deploy applications only on Openstack using HEAT

This specification covers enhancements to Murano core library to deploy
applications across different clouds, based on the cloud configuration
and the policies by cloud operator and/or by end user through user interface.

Murano is shipped with number of classes that represent common infrastructure
entities like Instance, Network etc. Those classes together are known as
Murano Core Library and are used by most applications to interact with
the underlying cloud. Currently those classes were written with only
OpenStack in mind and their implementation mostly relies on OpenStack Heat
API to create OpenStack resources. That makes it not sufficient for other
clouds where there is no such API available and entities not always have
the same properties as they have in OpenStack.

Murano should include support for the following clouds:
    * OpenStack (native)
    * VMWare
    * Amazon (EC2)