Added 12x16 font (stretched and smoothed from 6x8)
This latest release adds a new built-in font size of 12x16. The addition of the font doesn't increase the FLASH size because this font is derived from the 6x8 font and then a smoothing algorithm is applied which makes diagonal pixels look smoother (see readme for a photo of the effect). I also changed the font names to reflect the pixel sizes (e.g. FONT_SMALL -> FONT_6x8), but have retained the old constants to keep existing software working.