The ShowNoticeAction subclasses were cut-n-pasting a lot of prepare() code from ShowNoticeAction, though the only part that's different is how we look up the notice. Broke that out to a getNotice() method, so only that needs to be copied. Avoids extra copies of permission checks and other common code in this spot.
Numbered parameters when more than one used in a message.
L10n updates for consistency.
i18n for non-translatable exception.
Updated translator documentation.
Removed superfluous whitespace.
