Remove global ags object

[Aylur]

This is necessary for #107, beause the ags global object imported every service and as a side effect their dependent libraries had to be loaded.

Here is how to import everything

import Widget from 'resource:///com/github/Aylur/ags/widget.js'
import { Box, Button }  from 'resource:///com/github/Aylur/ags/widget.js'

import * as Utils from 'import * as Utils from 'resource:///com/github/Aylur/ags/utils.js';
import { execAsync, exec } from 'resource:///com/github/Aylur/ags/utils.js';

import App from 'resource:///com/github/Aylur/ags/app.js'
import Variable from 'resource:///com/github/Aylur/ags/variable.js'

// this is the base Service class that you want to subclass
// Service.Audio and other builtin services are no longer accessible like this
import Service from 'resource:///com/github/Aylur/ags/service.js'

// builtin services are at 'resource:///com/github/Aylur/ags/service/<lower-casename>.js'
import Audio from 'resource:///com/github/Aylur/ags/service/audio.js';

The wiki is already updated and longer mentions the ags object
Services are now the instances themselves and not a static wrapper class

// this is no longer valid
Audio.instance.connect();

// you should now do this instead
Audio.connect()

// if you have a callback like this
onClicked: Notificatitions.clear

// update it to
onClicked: () => Notificatitions.clear()

// or
onClicked: Notificatitions.clear.bind(Notifications)