Improve statistic on used gas

This raises the maximum number of gas mixes listed to 20 and also changes
the layout / design of the stats tab to make it much more attractive.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
More layout work for stats tab

This finally gets me something that I like. The way the different boxes
get resized seems pleasant and intuitive. And it appears to do the right
thing on all platforms (I learned that having different levels of layout
nested creates no vertical offset on Linux/KDE, but a very ugly offset on
Mac, for example).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: fix the tab order

I know this is being redone, but the messed up tab order was driving me
insane when testing.

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