ES5 → 7: Use enhanced object properties

http://es6-features.org/#PropertyShorthand

Instead of doing {"foo": foo, "bar": bar, ...}, we can just do
{foo, bar} now.

The function parameters of EventHandlers have all been renamed to
camelCase to make use of this, as the JS style conventions intend.
Other functions will follow in a later commit.

src/qml/UI.qml

@@ -64,11 +64,7 @@ Item {
             }
 
             function showRoom(userId, category, roomId) {
-                var info = rooms.getWhere({
-                    "userId": userId,
-                    "roomId": roomId,
-                    "category": category
-                }, 1)[0]
+                var info = rooms.getWhere({userId, roomId, category}, 1)[0]
 
                 pageStack.replace("Chat/Chat.qml", {"roomInfo": info})
             }