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/Chat/Banners/UnknownDevicesBanner.qml

@@ -20,9 +20,9 @@ Banner {
         }
     ]
 
-    buttonCallbacks: {
-        "inspect": button => {
+    buttonCallbacks: ({
+        inspect: button => {
             print("show")
         }
-    }
+    })
 }