Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/Attr.AllowedFrameTargets.txt

@@ -0,0 +1,12 @@
+Attr.AllowedFrameTargets
+TYPE: lookup
+DEFAULT: array()
+--DESCRIPTION--
+Lookup table of all allowed link frame targets.  Some commonly used link
+targets include _blank, _self, _parent and _top. Values should be
+lowercase, as validation will be done in a case-sensitive manner despite
+W3C's recommendation. XHTML 1.0 Strict does not permit the target attribute
+so this directive will have no effect in that doctype. XHTML 1.1 does not
+enable the Target module by default, you will have to manually enable it
+(see the module documentation for more details.)
+--# vim: et sw=4 sts=4