ADD: "Backend.App": Add methods to hide/show window, to bring it to the front.
ADD: Implement basic system tray icon menu support.
FIX: "Backend.App.TrayMenu": Refactor code, fix show message error.
Merge branch 'master' into python2.7

- ADD: Implement basic system tray icon menu support.
- ADD: "Backend.App": Add methods to hide/show window, to bring it to the front.