Added the option to use env variables in the configuration and Dropbox (for the ssh key file)

[drkostas]

• Changed configuration type to YAML with the option to use OS Env Variables
  1. Created a YAML Configuration Loader class
  2. Added the option to use OS Env Variables in the YAML
  3. Created the required schema of the YAML file (_ymlschema.json) and added validation in the init of the Configuration class
  4. Created Unittests for the Configuration class
• Using the argparse library for passing arguments to server.py which are:
  1. The path to the YAML file
  2. The path to the log file that is going to be created (optional)
  3. Run mode - options: _runflask (default), _createinstance or _uploadfile
     • run_flask: runs the flask server as usual (this is the default mode)
     • create_instance: runs the code from utilityScripts/createInstance.py
     • upload_key_file: Uploads the defined ssh key file to Dropbox
• Option for uploading the ssh key file to Dropbox added
  1. Created Dropbox class that handles the upload and the download of the ssh key file
  2. Created relevant run-mode for the server.py (upload_key_file)
  3. Created upload and download key_file functions in the server.py
  4. Created Unittests for the Dropbox class
  5. Automatically downloading the ssh key file when the configuration includes the cloudstore section and the run mode is run_flask
• Moved utilityScripts/createInstance.py into the server.py as it could be implemented as a single function
• Using the logging library for printing