Add package translation support

[rubenwardy]

Fixes #516 , fixes #507

Engine PR: minetest/minetest#14410

Steps:

• Add .tr file parser (to MinetestCheck, see where config parser is). With unit tests
• Add table for holding translations
• Show translations on view package
• Show translations on package lists on web interface
• Show translations on API, if passed locale info
• Optional: Create empty PackageTranslations based on all locale files, so Languages details is accurate
• Use translations when searching
• Add support for translating lang desc
• Removing a language .tr should clear/delete PackageTranslation

Remaining untranslated

• QueryBuilder: title sorting
• Donate: title sorting, title page
• Homepage query options
• Shields title
• User todo: title sorting, template
• Bulk support names (all_game_support)
• Profile: title sorting
• Stats
• Carousel
• Collections: create edit
• Collections: package_add_to.html
• Collections: view
• forms.html: package_lists()
• render_reviews
• threads: render_threadlist
• notification
• package pages titles and more
• threads list title
• thread title
• editor todo
• zipgrep view results