Start of "production videos", a.k.a. tagged assets overview

Tagged assets are shown in a list per tag. The list is dynamically
loaded with JavaScript.

cloud/tagged/routes.py

@@ -0,0 +1,16 @@
+import logging
+import datetime
+import functools
+
+from flask import Blueprint, jsonify
+
+blueprint = Blueprint('cloud.tagged', __name__, url_prefix='/tagged')
+
+log = logging.getLogger(__name__)
+
+
+@blueprint.route('/')
+def index():
+    """Return all tagged assets as JSON, grouped by tag."""
+
+