Path reordering command

Closes #1491 (closed)

This commands recomputes the orderings of all the ElementPaths of a single corpus using a temporary table. The temporary table helps save from 0% to 50% of the update time, depending on the state of the in-memory database cache. I ran this on every project in my local database and found that it took just under a millisecond for each path in the worst case (without any time save from the temporary table, and with every single ElementPath having to be updated!).