Remove the Claim Draw menu item

Instead, we should prompt the player when he has the option of claiming
a draw. This will come in the next commit.

https://bugzilla.gnome.org/show_bug.cgi?id=727345
Remove the gear menu

https://bugzilla.gnome.org/show_bug.cgi?id=727345
Switch to a Save As button

The standard Save is still available with Ctrl+S

https://bugzilla.gnome.org/show_bug.cgi?id=727345
Add a resign button

https://bugzilla.gnome.org/show_bug.cgi?id=727345