Helipads were not being shown for convention airports, only for
heliports. Fix this up so helipads work alongside runways at
conventional airports, when the selected aircraft is a helicopter.
Support for --carrier-abeam option, which places the aircraft
at the end of a downwind opposite the FLOLS.
Add launcher support for above.
Add carrier display for launcher showing position relative to
carrier.
Allow selecting carriers from scenarios, and starting at either a
parking position, or a distance offset from the FLOLS (effectively
a crude ‘on-final’)
Extend the —carrier startup option to accept a runway ident of FLOLS,
in conjunction with the existing —offset-distance argument.
Categorise arguments to ensure user-specified ones take precedence
over values set by the launcher.
When any positional arg is set, exclude all positional ones from being
set at all, to prevent strange interactions.
This simplifies the launcher's rendering since the widget-based
code is gone, various things get hooked up as a result. Styling
fixes everywhere as well.
Menubar on Linux/Windows needs to be re-added.
