3750 Filters and search should say CHOSE not CHOOSE regarding warnings

https://code.google.com/p/otwarchive/issues/detail?id=3750

Filters and work search said "Choose Not to Use Archive Warnings" when what we wanted was the warning_display_name, "Author Chose Not to Use Archive Warnings."

In related news, we should make that "Creator," not "Author."
Do you think it's worth resurrecting and updating the (currently unused) helper method ```label_for_filter``` (in ```tags_helper.rb```), which seems to have been designed for this purpose, but then forgotten? It would need updating to check for lowercase "warning", but then we could call ```label_for_filter(tag_type, {name: tag.name, count: tag.count})```.