Create a second block to allow a user with a 3rd access right (edit all tags) to delete unwanted / inappropriate tags

As said in the title, this creates another block that can be placed on the page and will only show if a user has certain access rights (an new permission to edit all tags).

This block is not for adding tags, but deleting should work as expected - removing all copies of the deleted tag on the current node (I've tested my code and found it works for me, so I will tidy it up a bit, and then if others could also test and review the code that would be appreciated).

Nathan