Improved attachments, auto-creation of attachment lists and shared folder of old attachments
Introduce better handling of attachments:
- Move attachments into own files (in _attachments folder) -- at least a xyz.html and additionally a xyz.script.html if necessary
- Introduce new block email_text to contain solely the mail text
- Generate all boilerplate like the tabs in _game_email.html based on the new_attachments list variable
- Keep old email block for downward compatibility and custom cases
Introduce "shared folder" for attachments:
- The folder is filled automatically from lists of old and new attachments
All emails now use the new automatic creation method for attachments based on separate files that allows reusing the files/attachments on the next pages (in the cloud/shared folder)