O2/He percentages aren't integral

We do gas mixes in permille, not in percent.  Some people really like
using the value they got from the analyzer, which is generally something
like 29.4% or whatever.  So don't truncate percentages to integers.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix the imperial cylinder size calculations in equipment handling

This makes us use the same linear calculations as we did in the Gtk
branch.  We don't take compressibility into account, since tank
manufacturers don't seem to either.  A Luxfer AL80 is 11.1 liters, and
with the standard (non-compressibility) calculations, 80 cuft of air at
3000 psi is 11.094 liter, so that is the right model to use.

Also, stop with the horrible "units in edited numbers" stuff.  It uses
up precious space, and doesn't look any better.  If the user asked for
cuft, give him cuft without making a big deal about it.

Oh, and if the working pressure doesn't exist, sizes are always in
liters.  That's what we did in the Gtk branch, that's what we do here.
Again, no reason to even bother stating units, it's not helping.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't show '0.0%' gas percentages

It's just distracting.  Leave it empty.  No helium should be visually
very different from actual trimix, and for oxygen, zero means something
different anyway (it's air).  In neither case is '0.0%' a good string to
show, just show it as empty.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Show sample pressures in the cylinder equipment page

If we don't have any manually set pressure data, show the data from the
samples instead.  It uses an italic font for this case, mainly because I
couldn't figure out how to gray things out.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>