File processing

Introducing the asset of type file creation. This involves making a
node collection entry of type asset, as well as a file collection
entry, plus all the needed variations if such file is an image or a
video. Further, depending on the storage backend (pillar or other) we
synchronise the files there using rsync. Currently this functionality
is available only via pillar-web, since a web interface is needed to
upload the file in a storage folder, which is shared between the two
applications.

pillar/manage.py

@@ -914,7 +914,7 @@ def import_data(path):
 
 @manager.command
 def make_thumbnails():
-    from application.file_server import build_thumbnails
+    from application.modules.file_storage import build_thumbnails
     files = db.files.find()
     for f in files:
         if f['content_type'].split('/')[0] == 'image':