Hygiene: Standardise on time i10n parameter

Change-Id: I6a5376ea131aea7cdcdefcdb71af4d8e415f9347
i18n: Allow translation of participants

Switch to using more generic i10n function
Use simpler message for plural handling - only used last author
and creator to avoid having to deal with edge cases where creator and
last 2 authors were the same person.

Dependency: I15c167f245ba0842fc77fb4e03e380c40784ee1b
Change-Id: Ia45427ddf74bb7b74c7dd5e341507b3cff065097