[XenDACH] LimitLanguageUsage

xF2 Add-on [XenDACH] LimitLanguageUsage 2.0.40

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[Add] Prevent for enabling/disabling default language during editing language
[Add] Prevent for disabling default language in ACP language list

Thanks for your help @nocte, again..
[Add] Prevent storing an invalid language via account / preferences
[Add] Prevent storing an invalid language via frontend language choose or id

[Fix] Style issue in acp language table