Refactoring of init.php

- fetching is now done by a global function in fetch.php. This
  allows to use this functions in test/xpath.php for testing.
- besides of user configuration as explained in README.d json
  files from `mods` are now also loaded and used for fetching
  articles
- loading of json files is done only one time and not for each
  article to process
- test/xpath.php is now a script, which can be used to test a
  configuration from `mods`-directory

Added two mods for 4players and visions.de.

TODO: rewrite README.md

fetch.php

@@ -0,0 +1,86 @@
+<?php
+
+//
+// Main global function for fetching and processing articles
+//
+function fetch_article($article, $config) {
+
+	// the only config type supported now is 'xpath'
+	if ($config['type'] != 'xpath')
+		return false;
+
+	$doc = new DOMDocument();
+	$link = trim($article['link']);
+
+	if (defined('VERSION') && version_compare(VERSION, '1.7.9', '>=')) {
+		$html = fetch_file_contents($link);
+		$content_type = $fetch_last_content_type;
+	} 
+	else {
+		// fallback to file_get_contents()
+		$html = file_get_contents($link);
+
+		// try to fetch charset from HTTP headers
+		$headers = $http_response_header;
+		$content_type = false;
+		foreach ($headers as $h) {
+			if (substr(strtolower($h), 0, 13) == 'content-type:') {
+				$content_type = substr($h, 14);
+				// don't return here to find LATEST (if redirected) entry
+			}
+		}
+	}
+
+	$charset = false;
+	if (!isset($config['force_charset'])) {
+		if ($content_type) {
+			preg_match('/charset=(\S+)/', $content_type, $matches);
+			if (isset($matches[1]) && !empty($matches[1])) $charset = $matches[1];
+		}
+	} else {
+		// use forced charset
+		$charset = $config['force_charset'];
+	}
+
+	if ($charset && isset($config['force_unicode']) && $config['force_unicode']) {
+		$html = iconv($charset, 'utf-8', $html);
+		$charset = 'utf-8';
+	}
+
+	if ($charset) {
+		$html = '<?xml encoding="' . $charset . '">' . $html;
+	}
+
+	@$doc->loadHTML($html);
+
+	if ($doc) {
+		$basenode = false;
+		$xpath = new DOMXPath($doc);
+		$entries = $xpath->query('(//'.$config['xpath'].')');   // find main DIV according to config
+
+		if ($entries->length > 0) $basenode = $entries->item(0);
+
+		if ($basenode) {
+			// remove nodes from cleanup configuration
+			if (isset($config['cleanup'])) {
+				if (!is_array($config['cleanup'])) {
+					$config['cleanup'] = array($config['cleanup']);
+				}
+				foreach ($config['cleanup'] as $cleanup) {
+					$nodelist = $xpath->query('//'.$cleanup, $basenode);
+					foreach ($nodelist as $node) {
+						if ($node instanceof DOMAttr) {
+							$node->ownerElement->removeAttributeNode($node);
+						}
+						else {
+							$node->parentNode->removeChild($node);
+						}
+					}
+				}
+			}
+			return $doc->saveXML($basenode);
+		}
+	}
+
+	return $article;
+}