appwindow: make sure tabs are not focusable

[pesader]

Fix issue #87.

[amezin]

Looking at GNOME Terminal source code:

It overrides notebook widget's grab_focus virtual method, and redirects it to the active terminal widget. And does not touch can-focus property.

I wonder if there is any practical difference (usually for UI I try to replicate GNOME Terminal - unless there are reasons not to do so).

[pesader]

Hey, sorry for disappearing! Classes are already at full speed, so I haven't had the time to make the changes you requested.

I saw you merged my PR already though. Will we keep it that way, or do you still prefer to reimplement the fix using GNOME Terminal's method?

[amezin]

I saw you merged my PR already though. Will we keep it that way, or do you still prefer to reimplement the fix using GNOME Terminal's method?

Currently, most of the UI is loaded from Glade (.ui) files. Overriding grab_focus will be a non-trivial change (even though moving from .ui files to just code seems to be the right direction). So I decided to accept it in this form for now.