Unifiy <xsl:output>-settings for web/ and admin/

<xsl:output>-settings must match web/ and admin/ as they share some templates.

added Bug Cleanup Confirmed Web labels

Since libxml v2.9.3 the following should generate the HTML5 "short" doctype:

<xsl:output method="html" doctype-system="about:legacy-compat" encoding="utf-8"/>

and since libxslt v1.1.30 the following should work fine too:

<xsl:output method="html" version="5" encoding="utf-8"/>

closed with commit fde95155