i18n-able-ize the [NEW] string

Done collaboratively as a teaching exercise!

Also changed the format a little - now a bolded text rather than
just a simple bracketed thing.

Bug: 43412
Change-Id: Ib1a623b7a17b33aaec6e83c99615a64172141c30
Fix typo
Merge branch 'master' of ssh://wmfgerrit/mediawiki/extensions/SemanticWatchlist