Translation updates and maintenance

[Niklp09]

@pyrollo

• Replaced ontime_clocks ABMs w/ nodetimers
• Removed intllib support + po files [and .po tools]
• Removed 0.4 compatibility code
• Added mt 5 tranlation support + new templates
• Added German translation
• Added translation support to font formspec
• Added luacheck + fixed luacheck warnings
• Fixed https://github.com/pyrollo/display_modpack/issues/51
• Fixed https://github.com/pyrollo/display_modpack/issues/48
• Fixed https://github.com/pyrollo/display_modpack/issues/45
• Fixed https://github.com/pyrollo/display_modpack/issues/47 (Note: needs a very up to-date itemframes version https://notabug.org/TenPlus1/itemframes/commit/9f17f744d75a6c70f84308f66cc8c0837b550dd1)
• Fixed some other nil crashes

[Niklp09]

Replaced by https://github.com/mt-mods/display_modpack/pull/1. Replying to emails or github notifications would be very helpful...