More layout container SSI hacking

I reworded the SSI for the site a little more yet. The key difference is that I noticed that $DOCUMENT_URI does not change inside the included template. Therefor, an extra variable to pass the requested page is not necessary. I can simply use $DOCUMENT_URI itself.

Thus, the pages now simply say

<!--#if expr="! $HAVE_TEMPLATE" --><!--#include virtual="/template.shtml" --><!--#else -->
Page content goes here
<!--#endif -->

Meanwhile, in template.shtml:

<!--#set var="HAVE_TEMPLATE" value="1"
--><!--#include virtual="$DOCUMENT_URI"
-->

Referenced in An era has come to an end.