Item12839: Use parm name suggested by MichaelDaum

Also add some security to the InstalledPlugins page.  Only list
REST handler information to admins.

Change the default to false,  so that the new rest rules
are applied by default.

git-svn-id: http://svn.foswiki.org/trunk@17724 0b4bb1d4-4e5a-0410-9cc4-b2b747904278