The get_lang_count(), get_lang_list(), and get_lang_desc_list() functions are
more or less ported from load_cfg.c. If we ever need these in any other JS
files, they should be moved to a load-lib.

Re-synchronized this code with sbbs_t::maindflts():
- Don't accept keys for settings we didn't display
- Remove support for Auto-Login by IP address (chopping block feature)
- This is even a tad better as a translated (to another language)
  UserDefaultsHdr string (if/when there is one) would be displayed
  immediately upon a new language file being selected

Fixed a bug where the user online's command shell was used as the default
rather than the selected user's command shell (thisuser).

Fixed a bug where 'None' was hard-coded rather than use the text.dat string.

No longer needs/loads text.js (use the hard-coded string IDs in sbbs v3.20)
for a little speed boost.