Localeapp roundtrip + fixes

This includes an overdue synchronization of plugin locales. To make
translation easier for non-developers, we keep the strings at localeapp,
which puts everything in one file. All plugins enabled by default are
therefore included in Foodsoft's locales.

plugins/messages/app/views/message_threads/show.haml

@@ -1,5 +1,5 @@
 - if @group.nil?
-  - title t '.other'
+  - title t '.general'
 - else
   - title @group.name