Improve uemis xml parsing a bit

Improve uemis xml parsing a bit

It looks like the "units.pressure" setting is only about the units that
things are *shown* in on the wrist computer: the units in the file are
always in bar (or rather, centi-bar).

Which is definitely the right thing to do, and means that we shouldn't
care about parsing the units setting.  It's purely about how something
is shown, not about parsing.

That's probably true of the other units too, but let's see when I have
more data to go on.

Also, parse water temperatures and tank pressure.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>