multishell - roughly working draft using multishell-list for completions

multishell - roughly working draft using multishell-list for completions

Workable, need to resolve pending issues:

- depends on flet - what do i need to do about that?
- adaptation of multishell-list to purpose needs doc update, maybe rethink
- likewise hacking of multishell-list-entries
- inhibit duplicates from organized listing, preferring detailed one
- get mouse click so it ~properly concludes minibuffer activity