enlarge font overview block to 4 lines

enlarge font overview block to 4 lines

Extend further to be able to feature:

- all 94 ASCII characters;
- uncommon extension examples for georgian, hebrew, arabic;
- many more currency signs (inspired by HTML sampler top row),
  grouped by rarity: common symbols first (last ones are new to Unicode:
  rupee in 6.0, ruble in 7.0), then other significant national symbols
  (assortment from <http://sheet.shiar.nl/unicode>);
- dingbats and technical symbols (mostly personal favourites),
  restrict to plane 0 for now (extended emoji have unreliable width);
- common key/control graphic representations (space, bs, option/alt,
  command, menu, enter, null; also playstation (or symbolics kb) shapes).