Instead of manually doing String::format("%d"/"%u") everywhere, let's have
a String API for this. It's just a wrapper around format() for now, but it
could be made more efficient in the future.
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
You open the configuration for an app like so:
auto config = CConfigFile::get_for_app("MyApp");
This will then open ~/MyApp.ini and parse it for you.
Immediately start using it in Minesweeper to load the field size and mine
count from a config file.
