Bitmap font for everything (optionally)

[tatjam]

This requires two big things:

• A font which has the unicode support we need and has small characters (at max 12 pixels height or so)
• Changing all the code to use bitmap fonts (should be pretty easy)
• Adjusting default sizes of UI elements so they make more sense with the new font
• Making a "font agnostic" set of functions for creating widgets so they automatically use the bitmap / truetype modes

This will achieve a way smaller and crisp GUI (kind of like Project Zomboid?), which could be useful for players with smaller screen or just anybody who wants to really use all screen real estate.

This should be optional because having really tiny GUI is not liked by everybody.