Smart TV support

[Jeroen-Veltmans]

Initial implementation for #23.

Added navigation with the TV remote.
Slightly optimized default TV UI.
Increased default idle timeout for TVs.
Some smaller bugfixes.

Known issues:

Tizen 4.0 and Tizen 5.0 do not work as of now, partly due to a bug in the polyfill. I opened an issue which can be tracked here: webcomponents/polyfills#565
For now, it can be bypassed on Tizen 4.0 by adding the following script BEFORE loading the polyfills:

<script nomodule>
    customElements = customElements || {};
    customElements.forcePolyfill = true;
</script>

For Tizen 5.0 you would need to add the above, but also remove every nomodule for the legacy scripts as it will not load them otherwise.

Tizen 2.4 doesn't even show the player at the moment.