Translated using Weblate (Chinese (China))
Translated using Weblate (German)

Fix typo
Translated using Weblate (Portuguese)
Add minetest.get_gametime() API function, that returns the number of seconds since the world was created.
Add fallback font support for some languages.
Run updatepo.sh
Add dummy and LevelDB database backends
Make it compile
Add message that LevelDB is not supported on Windows
Use STL containers instead of irr::core::list
Fix 'Unknown map backend' error when using Configure menu right after creating world
Add note about --migrate only working with minetestserver or --server
Make --migrate update world.mt too
Prevent ModMgr from deleting backend setting in world.mt
Use system-wide LevelDB instead of bundled one