Previously the weather dialog box and environment system had some confusion

Previously the weather dialog box and environment system had some confusion
between temperature at altitude vs. temperature at sea level.  The dialog
box asked for temperature at altitude which makes sense, but all the
internal crunching expected temperature at sea level.  However, it makes no
logical sense to specify the sea level temperature for different layers so
I changed the internal processing to work with temperature at altitude and
then derive an approximate sea level temperature at the end.

If you know the ground temperature, you can just enter this temperature
for the first boundary layer and the system should do the right thing.