Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/HTML.FlashAllowFullScreen.txt

@@ -0,0 +1,11 @@
+HTML.FlashAllowFullScreen
+TYPE: bool
+VERSION: 4.2.0
+DEFAULT: false
+--DESCRIPTION--
+<p>
+    Whether or not to permit embedded Flash content from
+    %HTML.SafeObject to expand to the full screen.  Corresponds to
+    the <code>allowFullScreen</code> parameter.
+</p>
+--# vim: et sw=4 sts=4