Localize library tags

* convert all tags to have a `tag` field corresponding to the query parameter, and `intlLabel` field that defines the title message for `FormattedMessage`
* define all the tag messages in a shared file so they can be included in multiple places.
* convert the `TagButton` to use `tag` for the `onclick` handler value, and localize `intlLabel` for the title.

In the library I’ve continued to use `tag.toLowercase()` even though all the tags are currently defined as lowercase. It’s safer, but currently not strictly needed.