As discussed on FreeBSD-ports@, limit the port to a selection of aircraft,
instead of providing every single aircraft available on Flightgear website.
Planes not provided here will have to be installed by hand.
This change will ease port's usability and maintenance.
Also, remove wrong ending 's' to aicraft in COMMENT and pkg-descr .
PORTNAME and port's directory will be fixed later.
Submitted by: Warren Block <email@example.com> via FreeBSD-ports@