Switched font to 16x16

I had a complaint about readability with the 8x8 font, and it's one I
didn't really disagree with. So I've doubled it. I tried a 12x12 but I
didn't find the results particularly satisfactory (the spacing just
looked ugly), nor did I find any good results with libtcod-font-maker
(which seems to be broken, and I know zero Java so fixing it myself is a
nonstarter).

16x16 is a better resolution to count on in the future anyhow,
especially if I want to do tiles at some point (though I'm also
considering a ZX-Spectrum look, as I've seen some indication it would
look very nice and appropriate with the way libtcod consoles work.)