Modifying a tag from Manage Tags page requires the following user actions

1. In manage_tags_page.php, click on tag name (link)
2. In tag_view_page.php, click on Update Tag button
3. In tag_update_page.php, change fields and click Update

Step 2 is not necessary if the admin knows that they want to edit the tag, we should allow going straight to the Tag Update page.