Update redaction progressbar to Bootstrap 3, refactor

Closes #103
Add soft hyphen to form label and don't escape it
Add to list filter options of attachments in admin
Add more logging task
Add all attachments for pdf conversion
Use constant time compare to check secret
Create event on attachment approval
Fix bug in general update_followers task
Remove task for follower updates on postal replies
Introduce templates for follower updates
Add test to count number tag in subject