WIP - issue #111

Hi @baedert

I have tried to add this thing to master. Despite I can't get Vala working with Gnome Shell 3.10 (no status bar at all, and other things I have tried with vala DO NOT work, so I think it's a vala issue), this should be the direction for the PR.

Actually, when you click on the close button of the window, it just minimizes, but it is accessible from the shell.

Anyway, I have a problem, where everytime I click the close button it there is a error:

```
(corebird:5058): GLib-GIO-ERROR **: Settings schema 'org.baedert.corebird' does not contain a key named 'minimize-when-close'
[1]    5058 trace trap (core dumped)  ./corebird
```

I have changed the xml with settings, copied to the `XDG_DATA_DIRS`, rebuild settings and check if it's there with `dconf-editor`, which is true, but I still have this problems.

Could you guide me if you have enough time?

Cheers,

Guillermo