Make terminal a little more useful

The patch adds the following features:

 - UTF-8 compliance
 - Most Vt102 escape codes, excluding double width/height lines
 - Fancy colors
 - Support for function keys, cursor keys, and editing keys
 - Tested with vttest and vim

Bugs

 - No autorepeat
 - No support for function keys with modifiers
 - Configuration hard-coded
 - Redraw is slow