Melchior FRANZ:

Melchior FRANZ:

Implement simple help system with global and aircraft specific dialogs:

The gui.nas changes have been discussed with Andy. All ac have a help dialog,
but some are empty. (This wouldn't have been necessary, as the system falls
back to the "Common Aircraft Keys" if an aircraft has no help defined, but an
empty dialog is less confusing and encourages to be filled with interesting
information.   :-)    I scanned all aircraft files for interesting performance
data and added some to the dialogs (stall speed, etc.) The Concorde and the
p51d have (over?)complete dialogs and can serve as examples. The format is
documented in $FG_ROOT/Nasa/gui.nas.

There is also a couple of other, minor fixes.

The following files have ugly MSDOS line endings:

  $FG_ROOT/Aircraft/Hunter/hunter{-2tanks,}-set.xml
  $FG_ROOT/Aircraft/A380/A380-set.xml

The Concorde-jsbsim.nas file is a useless copy of the real */nas file, which is
in Nasal/. I'was debugging the Concorde and wondered why changes to this file
had no effect ...
(Fixed Concorde in the help-ac.diff patch: don't use "interpol" keyword as
variable.)