refactor: Disable Categories

Created by: Mogge

Pullrequest

We do not want to use categories anymore. So they are removed from the post contribution form and the post view. Please test! For layout reasons I also removed the display of the language in the post view.

Issues

• fixes #4101 (closed)

Todo

• Please make a followup Issue to remove this Database field and remove data from the database in a migration. (See @ulfgebhardt comment below )
  • Issue for Categories out of Filter (See @ulfgebhardt comment below )
  • Issue for Categories below Posts (See @ulfgebhardt comment below )
  • Issue for Categories out of Database (See @ulfgebhardt comment below )
  • Issue for Categories out of Admin page ( @Tirokk )
• What we do with the import of old posts? ( @Tirokk )

Additional Informations

The "last“ version with categories is stored in branch before-categories-switch--off.