Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/URI.HostBlacklist.txt

@@ -0,0 +1,9 @@
+URI.HostBlacklist
+TYPE: list
+VERSION: 1.3.0
+DEFAULT: array()
+--DESCRIPTION--
+List of strings that are forbidden in the host of any URI. Use it to kill
+domain names of spam, etc. Note that it will catch anything in the domain,
+so <tt>moo.com</tt> will catch <tt>moo.com.example.com</tt>.
+--# vim: et sw=4 sts=4