override index: clarify this doc's purpose
Based on feedback by elukey.
<summary>
<p>
This is an index of the directives that are allowed in .htaccess files for
- each <directive module="core">AllowOverride</directive> setting. To
- determine the set of directives that your server configuration allows
+ various <directive module="core">AllowOverride</directive> settings,
+ organized by class. Its intended purpose is to help server administrators
+ verify the privileges they're granting to .htaccess users. For an overview
+ of how .htaccess works, see the
+ <a href="../howto/htaccess.html">.htaccess tutorial</a>.
+ </p>
+
+ <p>
+ To determine the set of directives that your server configuration allows
.htaccess users to use:
</p>
