Revised reminder_list_truncated string

Follow-up on revert commit for issue #2971, as we don't store recipients
in history anymore.

Affects issue #15470
Fix regression in filter_api.php

Commit c9bc0646d69b2e39cd5e48320be82a83d8e39ebc introduced a regression,
whereby the filter would exclude issues without bugnotes when using text
search.

This was caused by removal of left outer join between bugnote_table and
bugnote_text_table, which was in fact required because the join clause
fails to return any record when the bugnote_text_id is null (which is
the case when there are no bugnotes).

Thanks to user Kitzberger for reporting this and atrol for providing the
steps to reproduce.
Updated CREDITS file in preparation of 1.2.15 release
Bump version and update release notes for 1.2.15
Changed version to 1.2.16dev
Localisation updates from http://translatewiki.net.