Allow bulk renaming of distribution records in the Admin.

1. On the Admin's Distribution records screen, search on the name.
2. Use the new Rank filter at right to narrow to, say, species.
3. From the Action drop-down, select the Rename action.
4. On the next screen, enter the new name and press Rename.

Note: this does not warn if records already exist with the new
name, but no records are ever overwritten: at worst, there
could be some duplicate records. (#571)