* (bug 7918) Fix regression in display of "templates used on this page" for users...

* (bug 7918) Fix regression in display of "templates used on this page" for users with edit form before preview
* Make section edits show templates used in the section, not the page

Patch by Mark Haidar (Fyren).  I didn't change the Boolean params to class constants because they're currently called as ($this->preview, $this->section != ''), which is much more readable than the alternative.