Sets or gets the priority of a text tag.
Valid priorities are start at 0 and go to one less than number of tags. Each tag has a unique priority; setting the priority of one tag shifts the priorities of all the other tags to maintain a unique priority for each tag (but not imaged on the server side in this case). Higher priority tags "win" if two tags both set the same text attribute. When adding a tag, it will be assigned the highest by default; so normally the precedence of a set of tags is the order in which they were added.