Support (almost) complete @-code formatting through-out the terminal server

- bbs.expand_atcodes() now supports formatting (did not before this)
- text.dat/ini strings now support @-code formatting (did not before this)
  (this fixes issue #697)
- bbs.atcode() now supports more complete formatting (only supported -R/-L
  previously)

The -W (wide) formatting code is not supported in these cases since that code
currently sends UNICODE sequences directly to UTF-8 terminals, when used.