cleanup: Use method syntax

Modern javascript has a short-hand for function properties, embrace
it for better readability and to prepare for an eventual port to
ES6 classes.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/23

js/misc/params.js

@@ -2,7 +2,7 @@
 
 // parse:
 // @params: caller-provided parameter object, or %null
-// @defaults: function-provided defaults object
+// @defaults-provided defaults object
 // @allowExtras: whether or not to allow properties not in @default
 //
 // Examines @params and fills in default values from @defaults for