Make HUD the center widget in Flight view. Add menu item for map widget.
hud is a tool in VIEW_FLIGHT
MainWindow: handle maptool widget destroy event

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
MainWindow: make PFD the central widget.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Merge pull request #711 from koenkooi/widgets

Detach the map widget - rebase