Connect preferences to the rest of the code

The biggest problem here was that bool has different sizes in C and C++
code. So using this in a structure shared between the two sides wasn't a
smart idea.

Instead I went with 'short', but that caused problems with Qt being to
smart for its own good and not doing the right thing when dealing with
'boolean' settings and a short value. This may be something in the way I
implemented things (as I doubt that something this fundamental would be
broken) but the workaround implemented here (explicitly using 0 or 1
depending on the value of the boolean) seems to work.

I also decided to get rid of the confusion of where gflow/gfhigh are
floating point (0..1) and when they are integers (0..100). We now use
integers anywhere outside of deco.c.

I also applied some serious spelling corrections to the preferences
dialog's ui file.

Finally, this enables the code that selects which partial pressure graph
to show.

Still to do: font size, metric/imperial logic

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-gui.cpp

@@ -76,7 +76,7 @@ const char *getSetting(QSettings &s, QString name)
 	QVariant v;
 	v = s.value(name);
 	if (v.isValid()) {
-		return strdup(v.toString().toUtf8().constData());
+		return strdup(v.toString().toUtf8().data());
 	}
 	return NULL;
 }