[3.1.0] Deprecate addFilter; set up Filter namespace

- Added EXTERNAL dependency config-schema value
- Fix safe bug in Printer_HTMLDefinition
- Fixed broken smoketests

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1669 48356398-32a2-884e-a903-53898d9a118a

docs/dev-config-schema.html

@@ -133,6 +133,14 @@ Test.Example</pre>
           different, although they should offer the same functionality.
           If they are identical, use an alias instead.</td>
         </tr>
+        <tr>
+          <td>EXTERNAL</td>
+          <td>CSSTidy</td>
+          <td><em>Not shown</em>. Indicates if there is an external library
+          the user will need to download and install to use this configuration
+          directive. As of right now, this is merely a Google-able name; future
+          versions may also provide links and instructions.</td>
+        </tr>
       </tbody>
     </table>