Multi-language support

New method: bbs.load_user_text() to load/reload user's language file. The
user's select language file (if there is one) is automatically loaded upon
logon to the terminal server, but if the user changes their language
(e.g. via user_settings.js), we needed a way to force re-load of the language
text. This is the way.

bbs.text() now accepts an optional second (bool) argument that if true, will
return a string from the default language strings (in text.dat), and not a
string from any alternate language files (ctrl/text.*.ini) that might've been
loaded. This allows user_settings.js to always get the name of the default
language string (LANG), e.g. "English".