You'll need to copy these templates to the Twiki templates directory, and make
the following change in the 'edit' script to enable the 'apptype' directive:

<     TWiki::writeHeaderFull ( $query, 'edit', 'text/html', length($tmpl) );
---
>     my $CgiAppType = $query->param( 'apptype' ) || "text/html";
>     TWiki::writeHeaderFull ( $query, 'edit', $CgiAppType, length($tmpl) );
