Fix memory leak when switching providers within a playlist [Delivers #79305128 #79031288]

[Fixes #79305128 #79031288]
What about creating a field for all providers?? jwplayer.html5.default.js

var defaultProvider = {
        getName: function(state) {
                return "DefaultProvider";
        }

and extending it for youtube/video and new providers..

and then calling 

if (_currentProvider.getName() != Provider.getName())) {