Use window._paq instead of a local reference of _paq.

[luniki]

I traced back the problem of #5 that prevented the MediaAnalytics plugin from initializing:

• The Matomo plugin creates and writes to a local reference of window._paq to configure Matomo.
• As soon as Matomo is initialized it grabs the window._paq and replaces it: https://github.com/matomo-org/matomo/blob/d0e6442ccbd7cb4a6f8214731fdd9d70b4cea4bb/js/piwik.js#L7528
• Later the user wants to play the video. As soon as the video is ready to play, it wants to instruct Matomo to scanForMedia:

  paella-user-tracking/src/plugins/es.upv.paella.matomo.userTrackingDataPlugin.js

  Lines 145 to 147 in 0efda07

  	bindEvent(this.player, Events.STREAM_LOADED, () => {
  	_paq.push(['MediaAnalytics::scanForMedia']);
  	});

• Unfortunately this is only send to the local reference of the former value of window._paq. So it does nothing and the MediaAnalytics plugin never gets started.

There are several other potential occurrences of this problem. For example

paella-user-tracking/src/plugins/es.upv.paella.matomo.userTrackingDataPlugin.js

Lines 95 to 100 in 0efda07

	bindEvent(this.player, Events.COOKIE_CONSENT_CHANGED, () => {
	this.player.log.debug('Matomo: Cookie consent changed.');
	if (this.player.cookieConsent.getConsentForType(this.config.cookieType)) {
	// _paq.push(['rememberConsentGiven']);
	_paq.push(['rememberCookieConsentGiven']);
	}

[snoesberger]

Thanks for fixing this! I did test this PR with Opencast and now statistics data is also send for the media analytics plugin.

Unfortunately, the title information is still missing as I mentioned already here. In order to really benefit from the Media Analysis plugin, this issue needs to be solved: #8