Create tests for PSR-4 classes, refactor oldtests

[Art4]

The goal of this PR is to copy and revise as many tests as possible to test against the PSR-4 (namespaced) classes. The old tests for PSR-0 (without namespaces) will remain untouched if possible to ensure BC.

Update: After working my way through the oldtests folder, I decided to migrate these very old tests directly after all, to minimize future workload.

This PR relies on merging #722 and still needs some work.

This PR is a subtask of #731.

[Art4]

For the migration of the tests from the tests/oldtests folder I created a script to combine all test classes as an array for the PHPUnit data providers. The script is not perfect and I still had to fix a lot of lines with the multiline edit in my IDE. But it saved me a lot of work.

<?php
// change the foldername you want to migrate
$foldername = 'first_item_title';
$combined = '';
$path = dirname(__FILE__) . DIRECTORY_SEPARATOR . 'tests' . DIRECTORY_SEPARATOR . 'oldtests' . DIRECTORY_SEPARATOR . $foldername;

$files = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($path, FilesystemIterator::SKIP_DOTS));

foreach($files as $file_path => $info)
{
	$contents = file_get_contents($file_path);
	$contents = trim($contents);
	$contents = str_replace('Atom_03', 'Atom_0.3', $contents);
	$contents = str_replace('Atom_10', 'Atom_1.0', $contents);
	$contents = str_replace('DC_10', 'DC_1.0', $contents);
	$contents = str_replace('DC_11', 'DC_1.1', $contents);
	$contents = str_replace('RSS_09', 'RSS_0.9', $contents);
	$contents = str_replace('RSS_10', 'RSS_1.0', $contents);
	$contents = str_replace('RSS_20', 'RSS_2.0', $contents);
	$contents = str_replace('_Netscape', '-Netscape', $contents);
	$contents = str_replace('_Userland', '-Userland', $contents);
	$contents = str_replace(' extends ', '\' => [ extends ', $contents);
	$contents = str_replace('class ', "			'", $contents);
	$contents = str_replace('		$this->data =', "<<<EOT\n", $contents);
	$contents = str_replace("<?php\n", '', $contents);
	$contents = str_replace("\n?>", '', $contents);

	$combined .= $contents . "\n\n";
}

$combined = "<?php\n\t\treturn [\n" . $combined . "\n\n\t\t];\n";

file_put_contents($path . DIRECTORY_SEPARATOR . 'combined.php', $combined);

[Art4]

This PR is ready for review, but still relies on merging of #722.

[Art4]

I resolved all merge conflicts after merge of #722.

[mblaney]

In general I would say the copyright year shouldn't change when it's the only modification to a file, but all good for now.

[Art4]

Thank you. I agree with you in principle about the year but it was a follow up change from #727 to keep all headers consistent.