[3.0.0] Convert all $context calls away from references

- Update TODO list
- URISchemeRegistry doesn't return a reference for instance anymore, should do the same for other singletons

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1477 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/Injector.php

@@ -64,7 +64,7 @@ abstract class HTMLPurifier_Injector
      * @param $context Instance of HTMLPurifier_Context
      * @return Boolean false if success, string of missing needed element/attribute if failure
      */
-    public function prepare($config, &$context) {
+    public function prepare($config, $context) {
         $this->htmlDefinition = $config->getHTMLDefinition();
         // perform $needed checks
         foreach ($this->needed as $element => $attributes) {