ShellApp: Change activation API

Since almost all of the callers of shell_app_activate were using the
default workspace (by passing -1), remove that parameter.

Add a new shell_app_activate_full() API which takes a workspace as
well as a timestamp; previously we might have been ignoring event
timestamps from elsewhere.

https://bugzilla.gnome.org/show_bug.cgi?id=648149

js/ui/workspaceThumbnail.js

@@ -452,7 +452,7 @@ WorkspaceThumbnail.prototype = {
                                                  time);
             return true;
         } else if (source.shellWorkspaceLaunch) {
-            source.shellWorkspaceLaunch({ workspace: this.metaWorkspace,
+            source.shellWorkspaceLaunch({ workspace: this.metaWorkspace ? this.metaWorkspace.index() : -1,
                                           timestamp: time });
             return true;
         }