altosui: Fix Landed tab units

And clean up the whole flight value reporting code base. It would be
nice to create a separate class to make this easier; at present
there's a bunch of customization embedded in how values are presented
in each tab.

Reported by: Bdale Garbee <bdale@gag.com>
Signed-off-by: Keith Packard <keithp@keithp.com>