Create a client module for fuel-devops3.0

To reduce dependency issues and allow to re-use management layer of virtual/baremetal labs:

- separate all the code that manage environments nodes/networks into a 'devops' module
- separate all the code that provide a logical layer (ssh manager, filters for specific node roles, accessing to the services that are started on the environment nodes) into a fuel-devops client module.

Fuel-devops client module should provide a complete interface for interacting with the environment: manage nodes, mapping devops and nailgun nodes into a single object, accessing nodes via SSH, snapshot/revert nodes, bootstrap admin node and so on.
It should encapsulate some of methods from fuel-devops Environment object and fuel-qa EnvironmentModel object (then deprecate it later).