Link categories have a number of options associated with them that could be blog level options. Also, links could reuse the regular post categories for their purposes instead of having separate link-specific categories. Let's get rid of the linkcategories table, move the link category options into the options table and apply them uniformly to all links, and add a link2cat table for assocating links to categories. This allows us to get rid of the busy link-categories.php page entirely and reuse all of the post category stuff. Categories that have no links associated with them will be ignored when listing links by category.