Hide empty blocks

I would like to hide empty blocks from users. I am using taxonomy_block to highlight nodes that need editing, review, etc. I use taxonomy_access to control access to nodes based on some security terms. Taxonomy block already hides terms the current user is not allowed to see but the box is still present cluttering the screen. The attached patch allows a block to be hidden (via a per block option) if there are no terms in it. The patch also cleans up the save block interface so it does not reload to create and changes the button text slightly to make it less confusing (to me). It requires a new column to taxonomy_block (SQL included).