Selenium grid support

[mythsunwind]

Enables support for selenium grid if --nodeconfig <file> is given as an argument.

The <file> should be a JSON file containing the local address, the address of the hub and the capabilities. Example:

{
  "configuration": {
    "host": "192.168.10.185",
    "port": "9999",
    "url":  "http://192.168.10.185:9999",
    "register": true,
    "hubhost": "192.168.10.40",
    "hubPort": "4444",
    "maxSession": 1,
    "capabilities": [
      {
        "browserName": "Winium",
        "platformName": "Windows",
        "maxInstances": 1
      }
    ]
  }
}

I also added a new capability called resetDirectory. It can be used to remove files (cache files, settings etc.) in a given path at the start of a new session, so that the app always starts in the same state.

[sandraj-cuelogic]

@mythsunwind - I wanted to check with you about the above changes #183, if there is a working example that you can provide. It would be really helpful.

Awaiting your response regarding the same. Thanks. :)