Don't switch to a workspace when dragging it to launch on that workspace

With workspace thumbnails, we don't switch workspaces when dragging windows
between workspaces or adding new workspaces, so we also shouldn't switch
on launch.

 * Add workspace parameters to shell_doc_system_open(),
   shell_app_activate, shell_app_open_new_window()

 * Pass a 'params' object when activating items in the overview with
   two currently defined parameters: workspace and timestamp. (timestamp
   is only implemented where it is easy and doesn't require interface
   changes - using the global current timestamp for the shell is almost
   always right or at least good enough.)

https://bugzilla.gnome.org/show_bug.cgi?id=640996

js/ui/search.js

@@ -267,7 +267,7 @@ OpenSearchSystem.prototype = {
         return lang != null;
     },
 
-    activateResult: function(id) {
+    activateResult: function(id, params) {
         let searchTerms = this._terms.join(' ');
 
         let url = this._providers[id].url.replace('{searchTerms}', encodeURIComponent(searchTerms));