Add development requirements file to the contrib directory
Port and improve Event and EventNamespace classes from unstable branch
Update checkouts, documents and sources apps to use the new Event and EvenNamespace classes
Fix permissions of some of the web_theme app files
Use reverse_lazy to resolve the LOGIN_URL and LOGIN_REDIRECT_URL default views values
Remove remaked code that checked if a preview was zoomable via an API call
Clarify javascript code to determine if a preview is zoomable
Add new lazy-load class for fast drawing on interactive previews (Document page details view)
Remove invalid import
Improve document preview navigation in the document list view, the document page views and the smart link document preview view
Fix staging files previews, remove repeated and unused imports
Merge remote-tracking branch 'origin/development' into development