[LanguageSystem] WIP: Uses versionID now

* Added foreign keys
* Replaced contentID with contentVersionID (basically versionID)
[LanguageSystem] WIP: Fixed file ending
[LanguageSystem] WIP: Added cache classes
[LanguageSystem] WIP: Removed usage of {lang}

* {lang} isn't used anymore for the dynamic contents
* that is only valid for Contents as of now