Revert "remove htmlpurifier"

This reverts commit c21a462d52.

lib/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/CSS.MaxImgLength.txt

@@ -0,0 +1,16 @@
+CSS.MaxImgLength
+TYPE: string/null
+DEFAULT: '1200px'
+VERSION: 3.1.1
+--DESCRIPTION--
+<p>
+ This parameter sets the maximum allowed length on <code>img</code> tags,
+ effectively the <code>width</code> and <code>height</code> properties.
+ Only absolute units of measurement (in, pt, pc, mm, cm) and pixels (px) are allowed. This is
+ in place to prevent imagecrash attacks, disable with null at your own risk.
+ This directive is similar to %HTML.MaxImgLength, and both should be
+ concurrently edited, although there are
+ subtle differences in the input format (the CSS max is a number with
+ a unit).
+</p>
+--# vim: et sw=4 sts=4