Rename Launcher to ShellWindow

Towards sanity for shell/window/app/launcher.

* Remove app
* Rename app_name to app_title
* Set app_name as the application name when running an app
* Remove embedded attribute on applications
* Remove AppWindow.get_dialog which was unused
* Remove a couple of manual signal connections and use
  kiwis autoconnection

Change-Id: I63930f89f2583160f5e14a22771a2b5df70ff6c7