Added sizing and colour to the font class

Now you can pass a line size to the font render method, and it will
resize the characters.

You can also pass a colour.

Also, when initializing the font, you can specify monospace, or failing
that a width for the space character.
Starting to implement the font class in the menu

Not complete yet, still some bugs to work out.

I switched from rendering each menu option separately to rendering each
column as a whole, because I thought it might be simpler, but it isn't
really so I might switch back.

Also, I think kerning might be better handled within the font class. Set
sane defaults for leading/kerning/spacewidth, and allow overrides,
but measure kerning/spacewidth in character pixels instead of
render pixels.