- 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}"
            }]
        }
} 

• Major rework on the structure of the plugin. 
  • No blocks on the pages, only Login and Logout actions.
  • Cleaned up lots of obsolete or useless parameters
• Fixed life-cycle of the tokens, correctly requesting the access&refresh tokens on first usage, and using the refresh token when supposed to.
• Re-branded to Google Login Plugin (because this more about logging in than using Google Plus)