Symbols for Legacy Computing

• Fixes to all half, quarter and eights blocks, ░, ▒, ▓, ⍲, X, Ò, Ó, Ô,
  Õ, Ö, Ō, ō, Ŏ, ￩, ￪, ￫, ￬
• Make APL chars look nicer
• Adjust OS/2 metrics
• Set vertical advance to 0
• Added vertical metrics
  (https://fontforge.org/fontinfo.html#PS-General)
• Removed 🍺, 🍻, 💖, 💡, 😪
• Added ➥, ➦, Unicode 13 Symbols for Legacy Computing
• Sample rendering now includes blurred easily confused pairs
• Added sample generation using actual terminal software (on Linux) so
  that the README file shows a current version of the font.
• Branch cleanup (back to master/develop)