Add application menu.

Use menu model for left GtkMenuButton.

Use menu model for right edit menu.

Make buttons of header bar quadratic.

Fix typo in 'deamon'.

Fix sensitivity of "display daemon output" item.

Move UI definition to glade file, completely.

Fix mysterious bug that does not show app menu.

Set spacing to multiple of 6. Delete GtkAlignment.

Delete left menu button in HeaderBar.

Use set_app_menu() only for HeaderBar mode.

Use 16 pixel icon for ST button.
Use Action instead of signal handler in menus.
Add case distinction for different platforms.
Add GtkSeparator between menu bar and content.
Remove margins and add borders.
Fix bug with HeaderBar case distinction.
Use HeaderBar on any platform.
Merge branch 'menu' of https://github.com/jaystrictor/syncthing-gui into jaystrictor-menu

Conflicts:
	syncthing_gtk/app.py
Merge branch 'jaystrictor-menu'