Update Audio Engine to support new/future Chrome Behavior on Web Audio

[davrous]

Following Forum thread: www.html5gamedevs.com/topic/37632-audiocontext-error

Chrome will prevent audio from playing before any user gesture: https://bugs.chromium.org/p/chromium/issues/detail?id=840866#c103

We need to update the audio engine to follow Google's recommendations: https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#webaudio

[davrous]

Implementing suggestion from: https://sites.google.com/a/chromium.org/dev/audio-video/autoplay.
We will create the audioContext as soon as a sound object is created but it will be resume as soon as a user's interaction will be triggered. To know that the audioContext is muted, you need to check the state property that will be "running" if everything's ok otherwise will be set to "suspended". To unmute it, you need to call audioContext.resume() inside a user's interaction (click for instance).

[davrous]

Fixed via this PR: #5139