Refactoring of jobs and deployment parts

[gfieni]

PR overview :

• Cleaning functions and adding comments for 'Job' and 'Deployment' parts ;
• Moving flags value checks in the flags processing function ;
• Moving JSON requests from string to structures for marshal/unmarshal ;
• Moving the job reservation and node deployment parts in the driver to be able to reuse it easily ;
• Adding functions to wait until the job/deployment is finished ;
• Adding a function for getting a deployment informations from its id ;
• Removing the function for reading the ssh public key => use of golang 'ioutil.ReadFile' ;
• Updating README.

[mcolmant]

During test, docker-machine may blocks sometimes after the provisioning. After investigations, it does not seem to be related to the driver itself, but to the docker-machine command.