Correctly test QString for being empty

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
HTML export: fix packaging of theme dir

I was confused by the function name getSubsurfaceDataPath() - it does not
find paths relative to the "data" folder, if finds the path where we might
install folders like "data", "translations", or "theme".
"data" is for some reason where we install the "marbledata" files.
Therefore on both Mac and Windows we need to put the "theme" directory
next to the "data" directory, not below it.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix out of tree building without asciidoc

We tried to copy the .html.git file from the out of tree build dir, not
from the source dir.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Gas was printed in permille, use gasname instead

After the switch to a central event decoder and just return gasmix from
that we printed things in permille, eg. EAN1000 and 180/550 which looks
kinda strange.
This fixes that by using gasname instead to give the gas a name.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>