Fixes related to the REVERSED_CLIENT_ID parameter

Since we can now use a json file in the parent app to load the needed credentials to make the component work, we removed the variables section of the extensibility configurations. f you don't wan't to use the json file, just place the variables section in the extensibility configurations again:

{

    "plugin" :{

        "url": "https://github.com/andregrillo/cordova-plugin-googleplus.git",

        "variables": [

            {"name": "REVERSED_CLIENT_ID", "value": "xxxxxxxxxxxxxxxxxxxx"}

        ]

    }

}

- Improved error messages and descriptions

Code review and general improvements. Plugin revamp.

To enable the reuse of this plugin in multiple applications, we introduced a breaking change.

Take a look at these instructions 

With this update, you NEED to add to the Extensibility Configurations of your application with the following JSON:

{
    "plugin":
        {
            "url": "https://github.com/EddyVerbruggen/cordova-plugin-googleplus#5.0.3",
            "variables": [{
                "name": "REVERSED_CLIENT_ID",
                "value": "{iOS URL scheme}"
            }]
        }
}