luci-app-opkg: various improvements

 - Add additional filter option to hide translation packages
 - Add pager to top and bottom of package list (fixes #5671)
 - Add option to automatically install related translations along with
   LuCI packages
 - Add option to automatically install translations for all installed
   LuCI packages when installing a new language base package

Signed-off-by: Jo-Philipp Wich <jo@mein.io>