[core] extract BridgeAbstract methods to make them functions

- returnError, returnServerError, returnClientError ,debugMessage are
  moved to lib/error.php

- getContents, getSimpleHTMLDOM, getSimpleHTMLDOMCached are moved to
  lib/contents.php

Signed-off-by: Pierre Mazière <pierre.maziere@gmx.com>

lib/error.php

@@ -0,0 +1,30 @@
+<?php
+function returnError($message, $code){
+  throw new \HttpException($message, $code);
+}
+
+function returnClientError($message){
+  returnError($message, 400);
+}
+
+function returnServerError($message){
+  returnError($message, 500);
+}
+
+function debugMessage($text){
+  if(!file_exists('DEBUG')) {
+    return;
+  }
+
+  $backtrace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 3);
+  $calling = $backtrace[2];
+  $message = $calling['file'] . ':'
+    . $calling['line'] . ' class '
+    . $calling['class'] . '->'
+    . $calling['function'] . ' - '
+    . $text;
+
+  error_log($message);
+}
+
+?>