Use PSR-16 compliant caching

[jens1o]

We should use a PSR-16 compliant implementation for caching, where at the moment we use a simple cache from doctrine:

PHP-FFMpeg/src/FFMpeg/FFProbe.php

Lines 220 to 224 in 2649d45

	public static function create($configuration = array(), LoggerInterface $logger = null, Cache $cache = null)
	{
	if (null === $cache) {
	$cache = new ArrayCache();
	}

[jens1o]

psr-16 is more than enough for us, no need for psr-6. ;)

[jens1o]

done. Moved to Psr\SimpleCache while using Sabre's Memory Cache as a fallback. :)