Merge pull request #435 from 4teamwork/lg-disable-edit-border-for-extract-attachments

When saving attachments of e-mails, the menu "Edit" is show
Improved wording of German translations in extract attachments view.

Also renamed some i18n message IDs and defaults to better reflect their supposed message.
Added new mail event `AttachmentsDeleted`.
Synced translations for opengever.mail.
Journalize AttachmentsDeleted event.